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Question 1 Rapport
Which of the following is not a part of model rocket?
Détails de la réponse
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.
Question 2 Rapport
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?
Détails de la réponse
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.
Question 3 Rapport
Pilots uses aneroid barometer to know the height above sea level because
Détails de la réponse
Aneroid barometers are compact and lightweight, making them suitable for use in aircraft where space and weight are critical considerations. They provide a reliable measurement of altitude based on changes in atmospheric pressure.
Question 4 Rapport
Calculate the depth of a swimming pool if the apparent depth is 10cm. ( Refractive index of water = 1.33 )
Détails de la réponse
To calculate the real depth of a swimming pool given the apparent depth, we can use the concept of refraction of light. When light passes from one medium to a denser medium, it bends towards the normal. This bending effect causes objects submerged in water to appear closer to the surface than they actually are. The formula to relate these depths is given by:
Real Depth = Apparent Depth × Refractive Index
Given the problem:
Using the formula:
Real Depth = 10 cm × 1.33
Calculating the above:
Therefore, the depth of the swimming pool is 13.3cm.
Question 5 Rapport
A body is whirled in a horizontal circle at the rate of 800 revolutions per minute. Determine the angular velocity
Détails de la réponse
To determine the angular velocity of a body whirled in a horizontal circle at a rate of 800 revolutions per minute (rpm), we need to convert this to the standard unit of angular velocity, which is radians per second (rad/s).
Here’s how you can calculate it:
Now let's perform the conversion:
Rounding up the decimal to a consistent significant figure, the angular velocity is approximately 26.7π radians per second.
Question 6 Rapport
Détails de la réponse
In a series resonant circuit, the current flowing in the circuit is at its maximum. Let me explain why:
In a series resonant circuit, we have a resistor (R), inductor (L), and capacitor (C) connected in series with an AC source. At a particular frequency called the resonant frequency, these circuits exhibit some unique characteristics. This resonant frequency is determined by the values of the inductor and capacitor and is given by the formula:
f₀ = 1 / (2π√(LC))
At the resonant frequency:
Thus, in a series resonant circuit, when it is operating at its resonant frequency, the current flowing is at its maximum.
Question 7 Rapport
If a charge ion goes through a combined electric field E and magnetic field B, the resultant emergent velocity of the ion is
Détails de la réponse
The resultant emergent velocity of a charged ion moving through combined electric and magnetic fields can be derived from the condition where the electric force equals the magnetic force. This gives us the formula for the velocity v:
q E = qvB
v = EB (q will cancel out)
NOTE: When both fields are present, for the ion to move without deflection, the electric force must equal the magnetic force.
Question 8 Rapport
The acceleration of a free fall due to gravity is not a constant everywhere on the Earth's surface because
Détails de la réponse
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.
Question 9 Rapport
The value of R in the above circuit to make the galvanometer measure 2A is
Détails de la réponse
Given: Ig = 50mA = 0.05A, I to be measured = 2A, r = 2Ω , Is = I - Ig = 2 - 0.05 = 1.95A
Shunt(R) = IgIs x r
R = 0.051.95 x 10 = 0.2564Ω
Question 10 Rapport
Electrolysis can be investigated using
Détails de la réponse
When investigating electrolysis, the most relevant instrument from the list provided is the Voltameter. This is because the voltameter is specifically designed to measure the amount of substance that is deposited or consumed at electrodes during the electrolysis of an electrolyte. It functions based on the chemical change associated with the electric current passing through the electrolyte.
Here is a simple explanation of how electrolysis works and why a voltameter is useful:
Electrolysis is the process of using electricity to cause a chemical reaction, which is usually a decomposition reaction. This involves passing an electric current through an electrolyte (a substance containing free ions). These ions migrate towards electrodes, resulting in chemical changes. The key aspect to measure during electrolysis is the amount of material (e.g., metal or gas) that is deposited at the electrodes.
The Voltameter helps in understanding electrolysis because:
Voltmeter, Ammeter, and Galvanometer are not used primarily for investigating electrolysis:
Question 11 Rapport
The energy of light of frequency 2.0 x 1015 Hz is (h = 6.63 x 10−34 Js)
Détails de la réponse
To determine the energy of light given its frequency, we can utilize the formula:
E = h × f
Where:
E is the energy of the photon in joules (J)
h is Planck's constant, approximately 6.63 × 10-34 J·s
f is the frequency of light in hertz (Hz)
Given the frequency f = 2.0 × 1015 Hz, we can substitute the known values into our equation:
E = 6.63 × 10-34 J·s × 2.0 × 1015 Hz
To simplify the calculation, multiply the numerical parts and then add the indices of 10:
E = (6.63 × 2.0) × (10-34 × 1015)
E = 13.26 × 10-19 J
This can be approximated to 1.33 × 10-18 J. Thus, the energy of light with the given frequency is 1.33 × 10-18 J.
Question 12 Rapport
Under which conditions is work done
Détails de la réponse
In physics, the concept of work is defined as the process of energy transfer that occurs when a force makes an object move. The conditions for work to be done are:
Now, let's evaluate each scenario:
A man supports a heavy load on his head with hands: In this case, although the man is applying a force upward to support the load, the load does not move in the direction of the force he is exerting (upward). Hence, no work is done.
A woman holds a pot of water: Similar to the first scenario, the woman applies an upward force to hold the pot. However, the pot remains stationary, and there is no movement in the direction of the force. Thus, no work is done.
A boy climbs onto a table: Here, as the boy climbs, he applies a force to move himself upward onto the table. The movement is in the direction of the upward force he is applying. Therefore, work is done.
A man pushes against a stationary petrol tanker: In this scenario, although the man is applying a force to the tanker, it does not move. Because there is no movement in the direction of the force, no work is done.
Question 13 Rapport
The dimension of young's modulus,E is given by
Détails de la réponse
Young's modulus, denoted by E, is a measure of the stiffness of a solid material. It is defined as the ratio of stress to strain in a material that is behaving elastically. Stress is the force applied per unit area, and strain is the deformation experienced by the material in response to the applied stress.
Let's break down the dimensions for Young's modulus:
Stress: Stress is defined as force per unit area. Thus, the dimension of stress can be expressed as:
Stress = Force / Area
The dimension of force is given by mass × acceleration, i.e., Force = MLT-2 (where M is mass, L is length, and T is time).
The dimension of area is length × length = L2.
Therefore, the dimension of stress is:
Stress = (MLT-2) / (L2) = ML-1T-2
Strain: Strain is the ratio of the change in length to the original length and is dimensionless because it is a ratio of two lengths.
Thus, the dimension of strain is simply 1 (dimensionless).
Since Young's modulus is the ratio of stress to strain, its dimension is the same as that of stress. Therefore, the dimension of Young’s modulus E is:
ML-1T-2
Question 14 Rapport
Infra-red thermometers work by detecting the
Détails de la réponse
Infra-red thermometers work by detecting the radiation from the body and converting it to temperature. These thermometers are designed to measure the infrared radiation, also known as heat radiation, emitted by objects. All objects with a temperature above absolute zero emit infrared radiation. The thermometer's sensor captures this radiation and converts it into an electrical signal that can be read as a temperature measurement. This method allows for quick, non-contact temperature readings, which is why infrared thermometers are often used in medical settings, industrial applications, and more.
Question 15 Rapport
Mouth part adapted for piercing and sucking is found in
Détails de la réponse
The mouthpart adapted for piercing and sucking is found in the mosquito. Mosquitoes have a specialized mouth structure called a proboscis. This proboscis is long and slender, allowing mosquitoes to puncture the skin of their hosts and suck blood. The proboscis is a complex structure that contains several needle-like parts that make the piercing and sucking process efficient and effective.
Question 16 Rapport
According to kinetic theory of gases, the pressure exerted by the gas on the wall is equal
Détails de la réponse
According to the kinetic theory of gases, the pressure exerted by a gas on the walls of its container relates to the behavior and movement of its molecules. To understand how this pressure forms, let's explore the following essential concepts.
Molecules in a gas move rapidly and randomly in all directions. When these molecules collide with the walls of their container, they exert force due to the change in momentum during these collisions. The frequency and force of these collisions contribute directly to the pressure experienced by the container walls.
The **pressure** exerted by the gas can be described in terms of the rate of change of momentum imparted by the walls per second per unit area. This means that pressure is determined by considering how fast and how much the momentum of the gas molecules changes when they bounce off the container's walls, spread over a specific area and over time. In simpler terms, the faster and more frequently molecules hit the walls, and the higher their change in momentum, the greater the pressure is.
This explanation can be directly associated with the statement: "rate of change of momentum imparted by the walls per second per unit area", which accurately describes the concept of pressure in the context of the kinetic theory of gases.
Question 17 Rapport
Two tuning forks of frequencies 6Hz and 4Hz respectively are sounded together. The beat frequency is
Détails de la réponse
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.
Question 18 Rapport
Use the diagram above to answer the question that follows
The zone labelled II is called
Détails de la réponse
The zone labelled II is called the littoral zone.
To explain: The littoral zone is a part of a body of water that is close to the shore. It is typically characterized by abundant sunlight and nutrient availability, making it a highly productive area for aquatic plants and animals. This zone supports various forms of life such as algae, small fish, and invertebrates. The key feature of the littoral zone is its proximity to the shoreline, where sunlight can penetrate to the bottom, allowing for photosynthesis to occur.
Question 19 Rapport
Which of the following measuring instruments operates based on the heating effect of electric current?
Détails de la réponse
Hot wire ammeters measure current by detecting the heat produced in a wire due to the electric current flowing through it.
Question 20 Rapport
What will be the weight of a man of mass 60kg standing in a lift if the lift is descending vertically at 3ms2 ?
Détails de la réponse
To find the apparent weight of a man of mass 60 kg standing in a descending lift, we first need to understand the concept of apparent weight. Apparent weight is the force that the man feels as his weight due to the reaction of the lift floor on him. When the lift accelerates, the apparent weight changes from his actual weight.
In this case, the lift is descending with a constant velocity of 3 m/s2. Since the acceleration is downward, it means the lift is accelerating negatively compared to an upward acceleration.
The formula to find the apparent weight (Wapparent) when in a lift is:
Wapparent = m(g - a)
Where:
Substituting these values into the formula, we get:
Wapparent = 60 (9.8 - 3)
Calculating further:
Wapparent = 60 × 6.8
Wapparent = 408 N
The closest option to 408 N in the answers provided is 420 N. Therefore, the correct answer is 420 N.
Question 21 Rapport
A rectifier is a device that changes
Détails de la réponse
A rectifier is a device that changes alternating current (A.C) to direct current (D.C). Alternating current is the type of electrical current that changes direction periodically, while direct current flows in a single, constant direction.
Rectifiers are essential in numerous electrical devices, particularly those that require a stable and consistent power supply. For example, most electronic devices like mobile phone chargers, laptop adapters, and televisions operate on D.C. power, and rectifiers convert the household A.C. power supply to D.C. so that these devices can function properly.
In summary, a rectifier converts A.C., which is alternating power supply, into D.C., which is a steady flow of electricity in one direction, making it usable for electronic devices and various applications that require direct current.
Question 22 Rapport
The food nutrient with the highest energy value is
Détails de la réponse
Fat is the food nutrient with the highest energy value, providing 9 calories per gram, while carbohydrates and proteins provide 4 calories per gram.
Fat is the body's most concentrated source of energy, providing more than twice as much potential energy as carbohydrates or proteins.However, carbohydrates burn fastest in metabolism. Fats are a type of lipid. Lipids are a group of organic compounds that are insoluble in water but soluble in organic solvents. Fats are solid at room temperature, while oils are liquid at room temperature.
Therefore, the correct answer is option C.
Question 23 Rapport
Find the amount of current required to deposit 0.02kg of metal in a given electrolysis for 120 seconds. [electro chemical equivalent of the metal = 1.3 x 10−7 kgC−1 ]
Détails de la réponse
To determine the amount of current required, we need to use Faraday's laws of electrolysis. The first law states that the mass of the substance deposited at an electrode is directly proportional to the quantity of electricity (or charge) that passes through the electrolyte.
Here, we have:
According to Faraday's first law of electrolysis, the mass (\( m \)) can be calculated by the formula:
m = z \times I \times t
Where:
Rearranging the formula to solve for current \( I \):
I = \(\frac{m}{z \times t}\)
Substituting the given values into the formula:
I = \(\frac{0.02 \, \text{kg}}{1.3 \times 10^{-7} \, \text{kg/C} \times 120 \, \text{s}}\)
Calculating the denominator:
I = \(\frac{0.02}{1.56 \times 10^{-5}}\)
Solving for \( I \):
I = 1282.05 \, \text{A}
Thus, the appropriate amount of current required to deposit 0.02 kg of metal in 120 seconds is approximately 1.3 x 103 A.
Question 24 Rapport
Bile is a greenish alkaline liquid which is stored in the
Détails de la réponse
Bile is a greenish alkaline liquid that plays a crucial role in the digestive process, particularly in the digestion and absorption of fats. It is produced in the liver, but it is not stored there. Instead, the bile is transported to a small organ where it is concentrated and stored until the body needs it for digestion. This organ is the gall bladder.
The gall bladder stores the bile and releases it into the small intestine when food, especially fatty food, enters the digestive tract. This helps in breaking down the fats into smaller droplets, making it easier for enzymes to digest them.
To sum up, the gall bladder is the organ responsible for storing bile.
Question 25 Rapport
Newton's law of cooling is valid only for a
Détails de la réponse
Newton's Law of Cooling states that the rate of heat loss of an object is directly proportional to the difference in temperature between the object and its surroundings, provided that this temperature difference is small.
Therefore, this law is only valid within a small temperature range.
Question 26 Rapport
The degree of precision of a vernier caliper is
Détails de la réponse
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.
Question 27 Rapport
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
Détails de la réponse
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.
Question 28 Rapport
Which of the following structures enables the exchange of gases in insects?
Détails de la réponse
In insects, the structure responsible for the exchange of gases is the tracheae. Insects have a unique respiratory system where air is taken in through tiny openings called spiracles located on the surface of their body.
The air then travels directly into a network of tubes known as the tracheae. The tracheae branch out extensively throughout the insect's body, allowing oxygen to diffuse directly to the insect's tissues and cells. The carbon dioxide produced in the cells travels back through the tracheae and exits the body through the spiracles.
Other structures like the skin, Malpighian tubules, and flame cells have different functions:
Thus, the correct answer is the tracheae as they specifically enable the exchange of gases in insects.
Question 29 Rapport
The equivalent capacitance of the capacitors in the circuit above
Détails de la réponse
apacitance in parallel = one at the top + one under = 2C
The two in the middle are in series = C2
The equivalent capacitance of the capacitors in the circuit above = C2 + 2C = 52 C
Question 30 Rapport
Détails de la réponse
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.
Question 31 Rapport
The process of adding impurities to a semiconductor material to increase its conductivity is
Détails de la réponse
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.
Question 32 Rapport
A medium texture soil with high organic matter is
Détails de la réponse
A medium texture soil with high organic matter is best described as loamy soil. Here's why:
Loamy soil is a type of soil that is characterized by a balanced mixture of sand, silt, and clay particles. Because of this blend, loamy soil is not too coarse like sandy soil, nor is it too compact and dense like clay soil, making it a medium texture.
Moreover, loamy soil is renowned for its high organic matter content. This means that it contains a significant amount of decomposed plant and animal residues, which enrich the soil and provide essential nutrients for plant growth. This high organic content enhances the soil's fertility and structure, enabling it to retain moisture yet drain well, making it ideal for farming and gardening.
In conclusion, due to its balanced texture and richness in organic matter, loamy soil is the best fit for a medium-textured soil with high organic matter.
Question 33 Rapport
The simple form of the lead acid accumulator often has a negative pole of
Détails de la réponse
The simple form of the lead acid accumulator often has a negative pole of lead plate. In a lead-acid battery, the key components include two electrodes and an electrolyte. The **negative pole**, also known as the cathode during discharge, is typically made of **lead (Pb)**, which is in the form of a **lead plate**. When the battery is in use or discharging, this lead reacts with sulphuric acid (the electrolyte) to create lead sulfate.
To break it down further:
Thus, by analyzing the composition and reactions within a lead-acid battery, it is clear that the **negative pole** is made from a **lead plate**.
Question 34 Rapport
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
Détails de la réponse
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.
Question 35 Rapport
The gravitational force between two objects is 10N, what is the new value of the force if the distance between them is halved?
Détails de la réponse
The gravitational force between two objects is determined by Newton's Law of Universal Gravitation, which can be expressed by the formula:
F = G * (m1 * m2) / r²
where F is the gravitational force, G is the gravitational constant, m1 and m2 are the masses of the objects, and r is the distance between the centers of the two objects.
In this problem, it is given that the initial gravitational force is 10N. According to the formula, the gravitational force is inversely proportional to the square of the distance between the two objects.
So, if the distance between the objects is halved (i.e., r becomes r/2), then the new gravitational force F' can be calculated based on the relationship:
F' = G * (m1 * m2) / (r/2)² = G * (m1 * m2) / (r²/4) = 4 * (G * m1 * m2 / r²) = 4 * F
Since the initial force F was 10N, the new force F' when the distance is halved is:
F' = 4 * 10 = 40N
Thus, the new value of the gravitational force is 40N.
Question 36 Rapport
A light ray passing from air into water at an angle of 30º from the normal in air would
Détails de la réponse
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).
Question 37 Rapport
The total number of ATP produced during glycolysis is
Détails de la réponse
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.
Question 38 Rapport
A thick glass tumbler cracks when boiling water is poured into it because
Détails de la réponse
When boiling water is poured into a thick glass tumbler, the inner surface of the glass is suddenly exposed to a much higher temperature compared to the outer surface. Glass is a poor conductor of heat, which means it does not transfer heat quickly. As a result, the inside of the tumbler becomes hot and attempts to **expand quickly**, while the outside remains cooler and does not expand at the same rate.
**This uneven expansion** creates tension between the inner and outer layers of the glass. The inner surface tries to expand but is constrained by the cooler, rigid outer surface, which isn't expanding as much or as quickly. This stress and tension can lead to cracking.
Therefore, the correct reason a thick glass tumbler cracks when boiling water is poured into it is because **the inside expands more rapidly than the outside.**
Question 39 Rapport
An accumulator is 90% efficient. If it gives out 2700J of energy while discharging, how much energy does it take in?
Détails de la réponse
In order to find out how much energy the accumulator takes in, given that it is 90% efficient and gives out 2700J of energy, we can use the formula for efficiency:
Efficiency = (Useful Energy Output / Total Energy Input) × 100%
Given:
Efficiency = 90%
Useful Energy Output = 2700J
We need to calculate the Total Energy Input (how much energy the accumulator takes in). Rearranging the formula to solve for Total Energy Input, we get:
Total Energy Input = Useful Energy Output / Efficiency
Substitute the known values:
Total Energy Input = 2700J / 0.9
Calculate the input:
Total Energy Input = 3000J
Therefore, the accumulator takes in 3000J of energy.
Question 40 Rapport
When a charged ebonite rod is brought near a charged glass rod, there will be
Détails de la réponse
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.
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