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Pregunta 1 Informe
Which of the following is not a part of model rocket?
Detalles de la respuesta
When it comes to a model rocket, it is crucial to understand the different parts that make up the rocket and their functions:
Now, “Not recovery devices” is listed among the options. A recovery device is actually a part of a model rocket system. Common recovery devices include parachutes or streamers that deploy after the rocket reaches its peak altitude, allowing it to return safely to the ground. Such devices are indeed part of a model rocket design.
Therefore, the option “Not recovery devices” itself is not recognized as a part of a model rocket. Instead, the sentence is stating that they are not part of the main components, which implies it's indicative rather than being the name of a component. Hence, it does not pertain to a single component like the body tube, nose cone, or fins.
Pregunta 2 Informe
Inbreeding is highly discouraged in humans because it may
Detalles de la respuesta
Inbreeding is the process where closely related individuals, like cousins or siblings, mate and produce offspring. **This practice is highly discouraged in humans for several reasons, but a significant concern is the potential for an outbreak of hereditary diseases.**
Here’s why inbreeding is problematic:
Therefore, **to promote genetic diversity and reduce the risk of hereditary diseases in offspring, inbreeding is discouraged in human populations**. This way, offspring are less likely to inherit harmful genetic combinations that can lead to health problems.
Pregunta 3 Informe
The gravitational force between two objects masses 1024 kg and 1027 kg is 6.67N. Calculate the distance between them [ G = 6.6 x 10−11 Nm2 kg−2 ]
Detalles de la respuesta
To calculate the distance between two objects based on the gravitational force acting between them, we need to use the formula for gravitational force:
F = (G * m1 * m2) / r²
Where:
We need to compute r by rearranging the formula:
r² = (G * m1 * m2) / F
Therefore, the distance r is:
r = √((G * m1 * m2) / F)
Substitute the given values into the equation:
r = √((6.6 x 10-11 Nm²/kg² * 1024 kg * 1027 kg) / 6.67 N)
Calculating inside the square root:
G * m1 * m2 = 6.6 x 10-11 * 1024 * 1027 = 6.6 x 1040 Nm²
Then divide by the force:
6.6 x 1040 Nm² / 6.67 N = 0.99 x 1040 m²
Finally, calculate the square root:
r = √(0.99 x 1040)
r ≈ 1.0 x 1020 m
Therefore, the distance between the two objects is approximately 1.0 x 1020 m.
Pregunta 4 Informe
What is the colour of red rose under a blue light?
Detalles de la respuesta
To understand the color of a red rose under a blue light, we need to consider how we perceive color. Objects appear colored because they reflect certain wavelengths of light. A red rose appears red in white light because it reflects red wavelengths and absorbs others.
When you shine blue light on a red rose, the situation changes. A blue light primarily contains blue wavelengths. Since the red rose does not have red wavelengths to reflect anymore, and it cannot reflect blue light (as it absorbs it), the rose will appear to be the absence of any reflected wavelength visible to our eyes.
This means the rose will appear black under blue light, as black is perceived when no visible light is reflected into our eyes. Thus, the color of the red rose under a blue light is black.
Pregunta 5 Informe
A sonometer's fundamental note is 50Hz, what is the new frequency when the tension is four times the original?
Detalles de la respuesta
To solve this problem, we need to understand the relationship between tension and frequency in a sonometer wire. The frequency of a vibrating string, such as one in a sonometer, is directly proportional to the square root of the tension in the string. Mathematically, this relationship is expressed as:
f ∝ √T
Where f is the frequency and T is the tension. In the given problem, the original frequency is 50 Hz, and the tension is increased to four times its original value. Let's analyze how this change in tension affects the frequency:
- Original tension = T
- New tension = 4T
Substitute the new tension into the formula:
f_new = 50 Hz × √(4T/T)
Simplify the equation:
f_new = 50 Hz × √4
f_new = 50 Hz × 2
f_new = 100 Hz
Thus, when the tension is four times the original tension, the new frequency of the sonometer's fundamental note becomes 100 Hz.
Pregunta 6 Informe
The degree of precision of a vernier caliper is
Detalles de la respuesta
The degree of precision of a vernier caliper is actually the **smallest value** that the vernier scale can measure, which can be considered as the resolution or least count of the instrument. The degree of precision for most standard vernier calipers is 0.01 cm (or 0.1 mm). This means that the caliper can measure dimensions down to a hundredth of a centimeter.
To understand why this is the case, consider the construction of a vernier caliper:
This alignment allows more precise measurements than the main scale alone. If the vernier scale has 10 divisions which coincide over a length equal to 9 divisions on the main scale, then each division of the vernier scale represents an extra 0.01 cm. Therefore, it allows measuring smaller intervals between the main scale markings very precisely.
Thus, you won't find vernier calipers with a degree of precision of 0.005 cm, 0.1 cm, or 1.0 cm as options in standard practice for precise measurement tools.
Pregunta 7 Informe
A load of 300N is to be lifted by a machine with a velocity ratio of 2 and an efficiency of 60%. What effort will be applied to lift the load?
Detalles de la respuesta
To determine the effort needed to lift a load using a machine, we first need to understand some key concepts: **Load**, **Effort**, **Velocity Ratio** (VR), and **Efficiency**.
1. **Load** is the force or weight that needs to be lifted by the machine. In this case, the load is 300N.
2. **Velocity Ratio (VR)** is the ratio of the distance moved by the effort to the distance moved by the load. Given here as 2.
3. **Efficiency** of a machine is expressed as a percentage and is the ratio of the useful work output to the input work done by the effort. Here, the efficiency is 60% or 0.60 as a decimal.
The formula to calculate the **Effort** is derived from the relationship between these factors:
\[ \text{Efficiency} = \frac{\text{Mechanical Advantage (MA)}}{\text{Velocity Ratio (VR)}} \]
Where:
\[ \text{Mechanical Advantage (MA)} = \frac{\text{Load}}{\text{Effort}} \]
From the above, we have:
\[ \text{MA} = \text{VR} \times \text{Efficiency} \]
Replacing with the given values:
\[ MA = 2 \times 0.60 = 1.2 \]
Now, calculate the **Effort** using the relation:
\[ \text{Effort} = \frac{\text{Load}}{\text{MA}} \]
\[ \text{Effort} = \frac{300N}{1.2} = 250N \]
Therefore, the **Effort** needed to lift the load is 250N.
Pregunta 8 Informe
Photometer is used to measure
Detalles de la respuesta
A photometer is an instrument designed to measure the intensity of light. It is used to determine how much light is received over a particular area. Photometers are vital in various fields such as photography, astronomy, and laboratory science for ensuring that light levels are appropriate for specific applications.
The device operates by assessing the brightness or illumination coming from a light source and comparing it with a standard light. The measurement can be displayed in different units such as lumens or lux, depending on the context of the measurement.
While photometers are focused on the intensity of light, they do not measure kinetic energy of liberated electrons, the frequency of light, or the wavelength of light. These quantities are measured using other specialized instruments, such as spectrometers or frequency analyzers.
Pregunta 9 Informe
The total number of ATP produced during glycolysis is
Detalles de la respuesta
During the process of glycolysis, a single glucose molecule is broken down into two molecules of pyruvate. During this metabolic pathway, there is a net gain of adenosine triphosphate (ATP) molecules. To understand how many ATP molecules are produced, let's break it down step by step.
1. **Initial ATP Investment:** Glycolysis initially requires an investment of 2 ATP molecules to phosphorylate glucose and convert it into a more reactive form during the early stages of the glycolytic pathway.
2. **ATP Production:** As glycolysis progresses, a total of 4 ATP molecules are produced. This occurs in the later steps of the pathway where adenosine diphosphate (ADP) is phosphorylated to form ATP. This is known as substrate-level phosphorylation.
3. **Net ATP Gain:** To find out the net gain of ATP through glycolysis, simply subtract the initial ATP investment from the total ATP produced:
Net ATP = Total ATP produced - Initial ATP investment
Net ATP = 4 ATP - 2 ATP
Net ATP = 2 ATP
Thus, the net total number of ATP produced during glycolysis is 2 molecules.
Pregunta 10 Informe
A light ray passing from air into water at an angle of 30º from the normal in air would
Detalles de la respuesta
When light passes from one medium to another, such as from air to water, it bends or refracts. This phenomenon is described by Snell's Law, which states: n₁ * sin(θ₁) = n₂ * sin(θ₂), where:
The refractive index of air is approximately 1, and the refractive index of water is approximately 1.33. Given the angle of incidence in air is 30º:
Using Snell's Law:
1 * sin(30º) = 1.33 * sin(θ₂)
You will find:
sin(θ₂) = sin(30º) / 1.33
sin(θ₂) ≈ 0.5 / 1.33
sin(θ₂) ≈ 0.375
Now, solve for θ₂ by taking the inverse sine (arcsin):
θ₂ ≈ arcsin(0.375)
θ₂ ≈ 22.09º
Thus, when a light ray passes from air into water at an angle of 30º from the normal in air, it will make an angle less than 30º from the normal in water, approximately 22.09º. This is because the light ray bends toward the normal as it enters a denser medium (water).
Pregunta 11 Informe
Find the value of a capacitor with voltage 5V and 30C.
Detalles de la respuesta
To find the value of the capacitance, we need to use the formula for capacitance:
Capacitance (C) = Charge (Q) / Voltage (V)
In this problem, the charge (Q) is given as 30 Coulombs (C) and the voltage (V) is 5 Volts (V). We can plug these values into the formula:
C = 30 C / 5 V
Calculating the above expression gives:
C = 6 Farads (F)
Therefore, the value of the capacitor is 6 Farads.
Pregunta 12 Informe
Calculate the magnetic force on an electron in a magnetic field of flux density 10T, with a velocity of 3 x 107 m/s at 60º to the magnetic field (e = 1.6 x 10−19 C)
Detalles de la respuesta
The magnetic force on an electron in a magnetic field (F) = q v Bsinθ
B = 10T, q = 3 x 107 m/, θ = 60º and q = 1.6 x 10−19 C
F = 1.6 x 10−19 x 3 x 107 x 10 x sin 60º ≊ 4.162 × 10−11 N
Pregunta 13 Informe
At a pressure of 105 Nm−2 , a gas has a volume of 20m3 . Calculate the volume at 4 x 105 Nm−2 at constant temperature.
Detalles de la respuesta
In order to solve this problem, we can apply **Boyle's Law**, which states that the **pressure** and **volume** of a gas are inversely proportional at a constant temperature. Mathematically, this is expressed as:
P1V1 = P2V2
Where:
Rearranging the formula to solve for V2:
V2 = (P1V1) / P2
Substituting the given values:
V2 = (105 Nm-2 x 20 m3) / (4 x 105 Nm-2)
By calculating:
V2 = (2100 m3) / 4 x 105
V2 = 5 m3
Therefore, at a pressure of 4 x 105 Nm-2, the volume of the gas is 5 m3.
Pregunta 14 Informe
If a body in linear motion changes from point P to Q, the motion is
Detalles de la respuesta
When a body moves in a straight line from one point, such as point P, to another point, such as point Q, the motion is called Translational Motion. This kind of motion refers to an object moving along a path in which every part of the object takes the same path as a reference point. This means that if you follow any point on the body, it covers the same amount of distance in the same time frame as any other point.
Let's break down the other options:
In conclusion, since the body is moving from point P to point Q along a straight line, it exhibits Translational Motion.
Pregunta 15 Informe
The process of adding impurities to a semiconductor material to increase its conductivity is
Detalles de la respuesta
The process you are referring to is called doping. In simple terms, doping is the method of intentionally introducing impurities into an extremely pure semiconductor to change its electrical properties, which increases its conductivity.
Semiconductors, like silicon or germanium, are materials that have electrical conductivity between conductors (like metals) and insulators (like glass). By adding impurities, we can control and enhance their ability to conduct electricity. These impurities are atoms of other elements that either have more or fewer electrons in their outer energy levels compared to those in the semiconductor.
When you add impurities with more electrons, it creates an n-type semiconductor because of the extra *negative* charge carriers (electrons). Conversely, adding impurities with fewer electrons makes a p-type semiconductor, as it creates 'holes' which act as positive charge carriers.
This process of doping is essential for creating various semiconductor devices, like diodes, transistors, and integrated circuits, which are foundational components in all electronic devices. Hence, doping plays a crucial role in the functionality and efficiency of electronic systems.
Pregunta 16 Informe
An object is placed 25cm in front of a convex mirror has its image formed 5cm behind the mirror. what is the focal length of the convex mirror
Detalles de la respuesta
Object distance (u) = -25 cm (negative because the object is in front of the mirror)
Image distance (v) = +5 cm (positive because the image is behind the convex mirror)
Using 1f = 1u + 1v
1f = 1−25 + 15
f = 254 = 6.250cm.
Pregunta 17 Informe
One of these is not the use of an electroscope
Detalles de la respuesta
Measuring ionization current in air:
This is typically not a function of an electroscope. While it can detect charge, it does not measure ionization currents, which require specialized equipment like an ionization chamber.
Pregunta 18 Informe
An air force jet flying with a speed of 335m/s went past an anti-aircraft gun. How far is the aircraft 5s later when the gun was fired?
Detalles de la respuesta
To solve this problem, we need to determine how far the aircraft travels in the 5 seconds after it passes the anti-aircraft gun. The problem gives us two key pieces of information:
To find the distance traveled, we use the formula for distance:
Distance = Speed × Time
Plugging in the given values:
Distance = 335 m/s × 5 s
Calculating this, we get:
Distance = 1675 meters
This means the aircraft is 1675 meters away from the point where it passed the anti-aircraft gun after 5 seconds.
Pregunta 19 Informe
When a bus is accelerating, it must be
Detalles de la respuesta
When a bus is accelerating, it is primarily changing its velocity. This is because velocity is a vector quantity, which means it includes both the speed and the direction of the object's movement. Acceleration refers to any change in this velocity. Therefore, the bus could be increasing its speed, decreasing its speed (which is also known as deceleration), or changing its direction. All these aspects involve a change in velocity.
Let's break it down further:
Changing its Speed: If the bus is speeding up or slowing down, it results in a change in the magnitude of its velocity, contributing to acceleration.
Changing its Direction: Even if the bus maintains a constant speed, if it changes direction (like taking a turn), its velocity is altered because direction is a part of velocity. This results in acceleration.
Changing its Position: While a change in position happens during acceleration, it is not the defining feature of acceleration. An object can change its position even if it is moving with constant velocity and not accelerating.
So, the key component here for acceleration is the change in velocity, which encompasses changes in speed, direction, or both.
Pregunta 20 Informe
A body is pulled on a horizontal surface with a rope inclined at 30º to the vertical. If the effective force pulling the body along the horizontal surface is 15N, calculate the tension on the rope.
Detalles de la respuesta
In this problem, the tension in the rope results in a force that acts to pull the body along the horizontal surface. The rope is inclined at 30º to the vertical, which means it makes an angle of 60º with the horizontal since the total angle between vertical and horizontal is 90º.
To find the tension in the rope, we first understand that the component of the tension force acting along the horizontal surface is given by the formula:
F_horizontal = Tension * cos(θ)
Where:
Given that F_horizontal = 15N, we substitute into the equation:
15N = Tension * cos(60º)
We know that cos(60º) = 0.5, therefore:
15N = Tension * 0.5
To find the Tension, divide both sides of the equation by 0.5:
Tension = 15N / 0.5
Tension = 30N
Therefore, the tension in the rope is 30N.
Pregunta 21 Informe
The energy in a moving car is an example of
Detalles de la respuesta
The energy in a moving car is an example of kinetic energy.
To explain simply, **energy** is the ability to do **work** or cause **change**. There are different forms of energy, and **kinetic energy** is one of them. It is defined as the energy possessed by an object due to its motion.
When a car is moving, it possesses **kinetic energy** because its components are in **motion**. This motion energy allows the car to do tasks, such as transporting people or goods from one place to another. The faster the car moves, the greater its **kinetic energy**, and thus it can make a larger impact or do more work.
In contrast, energy forms like **mechanical energy** is a combination of both kinetic and potential energy; **electrical energy** is associated with electrical charge movement, while **potential energy** is related to the position or condition of an object (like a car parked on a hill). Therefore, the specific type of energy from a moving car is **kinetic energy**.
Pregunta 22 Informe
A practical application of total internal reflection is found in
Detalles de la respuesta
A practical application of total internal reflection is found in fiber optics.
To understand this, let's break it down:
When light travels from one medium to another (such as from glass to air), it changes direction. This is known as refraction. However, there is a phenomenon called total internal reflection which occurs when light is traveling within a denser medium towards a less dense medium (like from glass to air) and hits the boundary at an angle greater than a certain critical angle. Instead of passing through, the light is completely reflected back into the denser medium.
Fiber optics technology makes use of this principle. In fiber optics, light is transmitted along the core of a thin glass or plastic fiber. The core is surrounded by another layer called the cladding. This cladding has a lower refractive index than the core, which facilitates total internal reflection. As a result, the light continuously reflects internally along the length of the fiber, allowing it to travel long distances with minimal loss.
This property is harnessed in various applications such as in high-speed telecommunication systems, medical equipment like endoscopes, and other technologies that require the transmission of data over long distances with high efficiency.
Pregunta 23 Informe
The unit of impedance is
Detalles de la respuesta
The unit of impedance is Ohm, which is symbolized by the Greek letter Ω (Omega). In electrical circuits, impedance (Z) is a measure of opposition that a circuit offers to the passage of electric current when a voltage is applied. It is similar to resistance but extends to alternating currents (AC) and contains the effects of resistance as well as reactance (which accounts for capacitors and inductors).
Just like resistance, the unit of impedance is the ohm because they measure similar concepts; however, impedance also accounts for phase shifts between voltage and current, which are not considered in simple resistance. Ohm's Law is used in AC circuits as Z = V/I, where Z is impedance, V is voltage, and I is current. This relationship shows why the unit of impedance is the same as that of resistance.
Pregunta 24 Informe
The dimension of power is
Detalles de la respuesta
The dimension of power in physics is expressed in terms of the base units of mass (M), length (L), and time (T). Power is the rate at which work is done or energy is transferred over time, and it has the unit of watt (W) which is equivalent to one joule per second.
To derive the dimension of power:
1. Work has the dimension of energy, which is force applied over a distance. The dimension of work (or energy) is M L2 T-2 because force has the dimension M L T-2 and distance adds another L.
2. Since power is work done per unit time, you would divide the dimension of work by time (T).
Thus, the dimensional formula for power is:
M L2 T-3
Pregunta 25 Informe
When a charged ebonite rod is brought near a charged glass rod, there will be
Detalles de la respuesta
When a charged ebonite rod is brought near a charged glass rod, there will be attraction. This is because charged objects obey the fundamental principle of electrostatics, which states that opposite charges attract each other while like charges repel each other.
An ebonite rod typically acquires a negative charge when rubbed with fur, as it gains electrons. In contrast, a glass rod usually acquires a positive charge when rubbed with silk, as it loses electrons. Therefore, when these two objects, one negatively charged and the other positively charged, are brought near each other, the opposite charges will attract.
Pregunta 26 Informe
The formation of cilia and flagella in living cells is carried out with the help of
Detalles de la respuesta
The formation of cilia and flagella in living cells is primarily carried out with the help of **centrioles**.
Here's a simple explanation:
Centrioles are cylindrical structures made up of microtubules. They are found in eukaryotic cells and play a critical role in cell division and the organization of the cell's cytoskeleton. However, their role extends beyond this to the formation of the basal bodies which seed the growth of cilia and flagella.
Cilia and flagella are microscopic, hair-like structures that protrude from the surface of certain eukaryotic cells. They are primarily involved in movement. Cilia often work like tiny oars, moving fluid across the cell's surface or propelling single-celled organisms. Flagella are typically longer and move in a whip-like fashion to propel cells, such as sperm cells.
Here's how centrioles contribute to the formation of these structures:
1. **Basal Body Formation**: Each cilium or flagellum grows out from a structure known as a basal body. The basal body is derived from the centrioles. During this process, a centriole migrates to the cell's surface and acts as a nucleation site for the growth of microtubules, which in turn form the structural core of cilia and flagella.
2. **Microtubule Organization**: The centrioles help organize microtubules in a "9+2" arrangement, which is characteristic of cilia and flagella. This refers to nine pairs of microtubules forming a ring around two central microtubules, giving these structures both stability and flexibility for movement.
Thus, centrioles are crucial as they provide the groundwork for the formation and proper functioning of cilia and flagella. They ensure that these structures are assembled correctly and are able to carry out their roles in cell movement and fluid transport.
Pregunta 27 Informe
When thermal energy in a solid is increased, the change in state is called
Detalles de la respuesta
When the thermal energy in a solid is increased, the solid particles gain energy and begin to vibrate more vigorously. As the temperature rises, these particles eventually have enough energy to overcome the forces holding them in their fixed positions. This leads to a change of state from a solid to a liquid. This process is known as melting.
To further understand this, imagine an ice cube. As it absorbs heat, it gains energy, and the ice (which is a solid) starts to turn into water (which is a liquid). This transition is what we refer to as melting.
Thus, the term that describes this change of state, when a solid is heated and turns into a liquid, is melting.
Pregunta 28 Informe
Two tuning forks of frequencies 6Hz and 4Hz respectively are sounded together. The beat frequency is
Detalles de la respuesta
When two sound waves of slightly different frequencies are sounded together, they interfere with each other in such a way that the intensity of the sound alternates between loud and soft. This phenomenon is known as "beats". The number of beats heard per second is called the "beat frequency".
The beat frequency can be calculated by subtracting the frequency of one wave from the frequency of the other. Mathematically, it is represented as:
Beat Frequency (fbeat) = | f1 - f2 |
Where:
In this case:
Using the formula:
fbeat = | 6Hz - 4Hz | = | 2Hz | = 2Hz
Therefore, the beat frequency is 2Hz. This means that you would hear 2 beats per second when the tuning forks of frequencies 6Hz and 4Hz are sounded together.
Pregunta 29 Informe
The tangential force acting on an object that opposes it from sliding freely on the adjacent surface is called
Detalles de la respuesta
The tangential force acting on an object that opposes it from sliding freely on the adjacent surface is called the friction force.
Let me explain each of the options to clarify why friction force is the correct answer:
In summary, friction force is the force that acts to oppose sliding between surfaces in contact and acts tangentially, making it the correct answer.
Pregunta 30 Informe
A refrigerator uses 150W. If it is kept on for 336 hours non-stop, what is the energy consumed in KWh?
Detalles de la respuesta
To calculate the energy consumption of an appliance, you can use the formula:
Energy (in KWh) = Power (in kW) × Time (in hours)
First, convert the power rating of the refrigerator from watts (W) to kilowatts (kW). Since 1 kW is equal to 1000 W, you can convert 150W to kilowatts by dividing by 1000:
150 W = 0.150 kW
Next, calculate the energy consumed over the period the refrigerator is kept on, which is 336 hours. Use the formula:
Energy = 0.150 kW × 336 hours
Now, perform the multiplication:
Energy = 50.40 kWh
Therefore, when the refrigerator is kept on for 336 hours non-stop, it consumes 50.40 kWh of energy. This is the correct choice.
Pregunta 31 Informe
A cell of internal resistance of 2Ω supplies current through a resistor, X if the efficiency of the cell is 75%, find the value of X.
Detalles de la respuesta
To solve the problem, let's first understand the concept of efficiency in this context. Efficiency refers to the ratio of the useful power output to the total power output of a system. In simpler terms, it tells us how much of the power provided by the cell is being effectively used by the resistor, X.
Given that the cell has an internal resistance (r) of 2Ω and we need the efficiency to be 75%, we will follow these steps:
Efficiency (%) = (R / (R + r)) * 100
Where:
According to the problem, efficiency is 75%, so:
(X / (X + 2)) * 100 = 75
First, let’s eliminate the percentage by dividing both sides by 100:
(X / (X + 2)) = 0.75
Now, let's solve for X:
X = 0.75 * (X + 2)
X = 0.75X + 1.5
0.25X = 1.5
X = 1.5 / 0.25
X = 6 Ω
Hence, for the cell to have an efficiency of 75%, the value of the resistor X must be 6Ω.
Pregunta 32 Informe
Detalles de la respuesta
To understand when a vapor is considered saturated, it is crucial to consider the rates of two significant processes: evaporation and condensation. **Evaporation** is the process where liquid molecules escape into the vapor phase, and its rate is denoted as **y**. On the other hand, **condensation** is the process where vapor molecules return to the liquid phase, with its rate denoted as **x**.
A vapor is said to be **saturated** when the rate of evaporation of the liquid is equal to the rate of condensation of the vapor. In simpler terms, the number of molecules leaving the liquid to become vapor is exactly equal to the number of molecules returning from the vapor to the liquid.
In mathematical terms, this condition can be described as **x = y**. Under this condition, the system reaches a dynamic equilibrium, and the vapor pressure of the system is at its maximum for the given temperature. At this point, the vapor cannot accommodate any more molecules, and thus, the vapor is in a saturated state.
Pregunta 33 Informe
5 X 10−3 kg of liquid at its boiling point is evaporated in 20s by the heat generated by a resistor of 2Ω when a current of 10A is used. The specific latent heat of vaporization of the liquid is
Detalles de la respuesta
To solve this problem, we need to calculate the specific latent heat of vaporization of the liquid. The specific latent heat of vaporization, denoted as \(L\), is defined as the amount of heat required to convert 1 kilogram of a liquid into a gas at constant temperature and pressure. The formula for specific latent heat of vaporization is given by:
L = \(\frac{Q}{m}\)
Where:
First, we need to calculate the total heat energy \(Q\) generated by the resistor. The heat produced by an electrical resistor can be calculated using the formula:
Q = I^2Rt
Where:
Given:
Substituting these values into the formula for Q:
Q = (10^2) * 2 * 20 = 100 * 2 * 20 = 4000 J
Now that we have the total heat energy supplied, let's calculate the specific latent heat of vaporization:
Given that the mass \(m\) of the liquid evaporated is \(5 \times 10^{-3}\) kg, we can substitute the values into the formula for \(L\):
L = \(\frac{4000}{5 \times 10^{-3}} = \frac{4000}{0.005} = 800,000 J/kg\)
Therefore, the specific latent heat of vaporization of the liquid is 8.0 x 105 J/kg.
Pregunta 34 Informe
An electron falls from an energy level of -5.44eV to another energy level, E. If the emitted photon is of wavelength 5.68 x 10−6 m, calculate the energy change. [ Plank's constant = 6.63 x 10−34 Js, emitted radiation speed = 3.0 x 108 ms−1 ]
Detalles de la respuesta
To find the energy change when an electron falls from one energy level to another, we need to calculate the energy of the emitted photon. This energy can be found using the formula:
E = hν or E = hc/λ
where:
Substitute these values into the equation:
E = (6.63 x 10-34 Js) * (3.0 x 108 ms-1) / (5.68 x 10-6 m)
First, calculate the numerator:
(6.63 x 10-34) * (3.0 x 108) = 1.989 x 10-25 J·m
Then, divide by the wavelength:
E = 1.989 x 10-25 J·m / 5.68 x 10-6 m = 3.5 x 10-20 J
Therefore, the energy change when the electron falls is approximately 3.5 x 10-20 J.
Checking the options provided, the closest value is 3.49 x 10-20 J.
Pregunta 35 Informe
The part of the inner ear that is responsible for hearing is
Detalles de la respuesta
The part of the inner ear that is responsible for hearing is the cochlea.
The inner ear is a complex structure, and each of its components serves different functions. Let me break it down further:
Thus, the cochlea is the crucial component of the inner ear responsible for converting sound vibrations into nerve signals, making it central to the process of hearing.
Pregunta 36 Informe
A hydrometer of mass y kg and volume 2y x 10−5 m3 floats in a fluid with 20% of its volume above the fluid, what is the density of the fluid?
Detalles de la respuesta
To find the density of the fluid, we need to apply the principle of floatation, which states that the weight of the fluid displaced by the submerged part of the object is equal to the weight of the object. Let's walk through the steps:
Step 1: Understand the volume submerged
The hydrometer has a total volume of 2y x 10-5 m3. It floats with 20% of its volume above the fluid. Hence, 80% of its volume is submerged in the fluid.
Submerged Volume, Vsub = (0.80) x (2y x 10-5 m3) = 1.6y x 10-5 m3
Step 2: Apply the principle of floatation
The weight of the fluid displaced equals the weight of the hydrometer.
Weight of hydrometer = Mass x Gravity = y kg x g (where g is the acceleration due to gravity). For the purpose of calculations, g can be considered as 9.81 m/s2.
Weight of displaced fluid = Density of fluid (ρfluid) x Submerged Volume x g
According to the principle of floatation:
y x g = ρfluid x 1.6y x 10-5 m3 x g
g is common on both sides and can be canceled out:
y = ρfluid x 1.6y x 10-5
Step 3: Solving for the density of the fluid
ρfluid = y / (1.6y x 10-5)
The y on both numerator and denominator cancels out:
ρfluid = 1 / (1.6 x 10-5)
ρfluid = 6.25 x 104 kg/m3
Thus, the density of the fluid is 6.25 x 104 kg/m3.
Pregunta 37 Informe
The velocity ratio of an inclined plane at 60º to the horizontal is
Detalles de la respuesta
The concept of an inclined plane is all about simplifying the forces involved in moving or holding a load. The **velocity ratio (VR)** for an inclined plane is defined as the ratio of the distance moved by the effort to the distance moved by the load. This can also be expressed in terms of the lengths involved in the triangle made by the inclined plane.
For an inclined plane placed at an angle **θ** to the horizontal, the velocity ratio is given by the formula:
VR = 1/sin(θ)
Given that the inclined plane is at an angle of **60º**:
First, find the sine of 60º:
sin(60º) = √3/2 (approximately 0.866)
Now, substitute this value into the formula for VR:
VR = 1/sin(60º) ≈ 1/0.866 ≈ 1.155
The **velocity ratio** for an inclined plane at **60º** to the horizontal is **approximately 1.155**.
Pregunta 38 Informe
I It wets glass
II It needs to be coloured
III It has a low density
Water is not suitable for use as a thermometric liquid because
Detalles de la respuesta
Water is not suitable for use as a thermometric liquid because:
a) It wets glass: This can cause issues with reading the level of the liquid.
b) It needs to be coloured: Water is typically clear, making it difficult to see the level without coloring.
c) It has a low density: This can affect the sensitivity and accuracy of the thermometer.
Pregunta 39 Informe
The acceleration of a free fall due to gravity is not a constant everywhere on the Earth's surface because
Detalles de la respuesta
The elliptical shape of the Earth: The Earth is not a perfect sphere; it is slightly flattened at the poles and bulging at the equator. This shape causes variations in gravitational acceleration.
Pregunta 40 Informe
Calculate the quantity of heat for copper rod whose thermal capacity is 400Jk−1 for a temperature change of 60ºC to 80ºC
Detalles de la respuesta
To calculate the quantity of heat absorbed or released by a substance, we can use the formula:
Q = C × ΔT
where:
Given:
First, calculate the change in temperature:
ΔT = Final temperature - Initial temperature = 80°C - 60°C = 20°C
Now, substitute the values into the formula to find the quantity of heat:
Q = 400 J/°C × 20°C
Calculate the answer:
Q = 8000 J
Since the options provided are in kilojoules (KJ), we need to convert joules (J) to kilojoules (1 KJ = 1000 J):
Q = 8000 J ÷ 1000 = 8 KJ
Therefore, the quantity of heat for the copper rod, given the specified conditions, is 8 KJ.
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