JAMB UTME - Physics - 2018
Frage 1 Bericht
A ball of mass 800g moving horizontally with a speed of 5m/s hits a vertical wall and rebounds with the same speed. The impulse experienced by the ball is?
Antwortdetails
The impulse experienced by the ball can be calculated using the principle of conservation of momentum, which states that the total momentum before the collision is equal to the total momentum after the collision. In this case, the momentum of the ball before the collision is:
p1 = m * v1
where m is the mass of the ball and v1 is its velocity before the collision. Substituting the values given in the problem, we get:
p1 = 0.8 kg * 5 m/s = 4 kg m/s
After the collision, the ball rebounds with the same speed but in the opposite direction, so its velocity after the collision is:
v2 = -5 m/s
The momentum of the ball after the collision is:
p2 = m * v2
Substituting the values, we get:
p2 = 0.8 kg * (-5 m/s) = -4 kg m/s
The negative sign indicates that the direction of the momentum is opposite to that before the collision.
The change in momentum of the ball is given by:
Δp = p2 - p1
Substituting the values, we get:
Δp = (-4 kg m/s) - (4 kg m/s) = -8 kg m/s
The negative sign indicates that the impulse experienced by the ball is in the opposite direction to its initial momentum, which is the direction of the wall. Therefore, the impulse experienced by the ball is 8 kg m/s.
Therefore, the correct option is: 8kgm/s.
Frage 2 Bericht
Which of the following does NOT describe the Image formed by a plane minor?
Antwortdetails
The option that does NOT describe the image formed by a plane mirror is "Magnified".
When an object is placed in front of a plane mirror, the image formed is:
1. Erect: The orientation of the object in the mirror is the same as the orientation of the object in real life. For example, if you raise your right hand in front of a plane mirror, the image in the mirror will also show your right hand raised.
2. Laterally inverted: The image formed in the mirror is flipped horizontally, which means that the left side of the object appears on the right side of the image and vice versa. For example, if you wear a shirt with the letter "H" on it and look at it in a plane mirror, the image will show the letter "H" flipped horizontally.
3. Same distance from the mirror as object: The image formed in the mirror is located behind the mirror at the same distance as the object is located in front of the mirror. For example, if you stand 1 meter away from a plane mirror, the image of yourself will also be located 1 meter away from the mirror, behind the mirror.
4. NOT magnified: The image formed in the plane mirror is of the same size as the object, which means that there is no magnification or reduction in the size of the image. For example, if you stand in front of a plane mirror with a height of 1 meter, the image of yourself in the mirror will also have a height of 1 meter.
Therefore, the correct answer is "Magnified", as the image formed by a plane mirror is not magnified.
Frage 3 Bericht
The time rate of loss of heat by a body is proportional to the
Antwortdetails
The correct answer is "difference in temperature between the body and its surroundings."
When a body is at a higher temperature than its surroundings, it will lose heat to the surroundings until it reaches thermal equilibrium, i.e., until the temperatures of the body and its surroundings are equal. The rate at which the body loses heat is proportional to the temperature difference between the body and its surroundings. This is known as Newton's law of cooling.
The law of cooling applies to a wide range of situations, from the cooling of hot beverages to the cooling of electronic devices. It is important to understand this law because it allows us to predict how long it will take for a body to cool down to a certain temperature, and to design systems that can regulate the temperature of a body, such as heaters or refrigerators.
Frage 4 Bericht
A body of mass 100g moving with a velocity if 10ms-1 collides with a wall. If after collision it moves with a velocity of 2.0ms−1 in the opposite direction, calculate the change in momentum.
Antwortdetails
Momentum = Mass x Velocity
Change in Momentum = Mass x (change in velocity)
Change in Momentum = Mass x (v - u)
Mass = 100g = 0.1kg
U = 2ms−1
V = 10ms−1
Change in momentum = m (v − u)
= 0.1 (10 − 2)
= 0.1 (8)
= 0.8Ns
Change in Momentum = Mass x (change in velocity)
Change in Momentum = Mass x (v - u)
Mass = 100g = 0.1kg
U = 2ms−1
V = 10ms−1
Change in momentum = m (v − u)
= 0.1 (10 − 2)
= 0.1 (8)
= 0.8Ns
Frage 5 Bericht
Mercury which is spilled onto a glass surface forms ball-like shapes because____.
Antwortdetails
In case of small drops of mercury, the gravitational potential energy is negligible in comparison to the potential energy due to surface tension.Consequently, to keep the drop in equilibrium, the mercury drop’s surface tends to contract so that its surface area will be the least for a sphere and the drops will be spherical.
But in the case of bigger drops of mercury, the potential energy due to gravity is predominant over the potential energy due to surface tension.Consequently, to keep equilibrium , the mercury drop tends to assume minimum potential energy as possible, the drop becomes oval in shape and lower center of gravity.
But in the case of bigger drops of mercury, the potential energy due to gravity is predominant over the potential energy due to surface tension.Consequently, to keep equilibrium , the mercury drop tends to assume minimum potential energy as possible, the drop becomes oval in shape and lower center of gravity.
Frage 6 Bericht
The resistance of a 40W car head lamp, drawing current from a 12V battery is ____.
Antwortdetails
The resistance of a 40W car headlamp can be calculated using Ohm's Law, which states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points, and inversely proportional to the resistance (R) of the conductor. The equation can be written as V = IR.
Since the power (P) of the headlamp is given as 40W and the voltage is 12V, we can calculate the current using the equation P = IV. Substituting I = P/V, we get I = 40/12 = 3.33A.
Finally, using Ohm's Law, we can calculate the resistance as R = V/I = 12/3.33 = 3.6Ω.
So, the resistance of the 40W car headlamp, drawing current from a 12V battery, is 3.6Ω.
Frage 7 Bericht
The force between the molecules of a liquid in contact with that of a solid is?
Antwortdetails
(ii) Adhesion : The force of attraction between unlike molecules, i.e. between the molecules of different liquids or between the molecules of a liquid and those of a solid body when they are in contact with each other, is known as the force of adhesion. This force enables two different liquids to adhere to each other or a liquid to adhere to a solid body or surface.
Frage 8 Bericht
The tendency of a body to remain at rest when a force is applied to it is called.
Antwortdetails
The tendency of a body to remain at rest or to continue moving with a constant velocity (in a straight line at a constant speed) when no force is acting on it is called inertia. Inertia is a property of matter, and the amount of inertia depends on the mass of an object. Inertia can also be thought of as a resistance to changes in motion, meaning that an object at rest will tend to stay at rest, and an object in motion will tend to stay in motion unless acted upon by an external force. This property of inertia is what makes it difficult to start, stop, or change the direction of motion of an object. The force required to overcome the inertia of an object depends on the mass of the object and the magnitude of the acceleration desired. Therefore, the greater the mass of an object, the greater its inertia, and the more force required to change its motion.
Frage 9 Bericht
Musical instruments playing the same note can be distinguished from one another owing to the difference in their
Antwortdetails
Different musical instruments playing the same note can be distinguished from one another due to the difference in their "timbre" or "tone color." Timbre refers to the unique character or quality of a sound that allows us to distinguish it from other sounds even when they have the same pitch and loudness. For example, a piano and a guitar playing the same note will sound different due to the differences in their timbre. This is why we can tell the difference between different instruments and why some instruments are better suited to certain styles of music than others.
Frage 10 Bericht
A narrow beam of white light can be split up into different colours by a glass prism. The correct explanation is that
Antwortdetails
The correct explanation for why a narrow beam of white light can be split up into different colors by a glass prism is that different colors of white light travel with different speeds in glass.
White light is made up of different colors with different wavelengths, ranging from violet to red. When a narrow beam of white light passes through a glass prism, the different colors refract at slightly different angles due to the fact that their wavelengths are different. This causes the different colors to spread out and form a spectrum.
The amount of refraction that occurs depends on the speed of light in the medium. Different colors of light have different speeds in glass due to the fact that their wavelengths are different. This means that they will refract at different angles as they pass through the glass prism, causing them to spread out.
So, the correct explanation for why a narrow beam of white light can be split up into different colors by a glass prism is that different colors of white light travel with different speeds in glass. Therefore, is the correct explanation.
is incorrect because it describes what white light is made up of, but does not explain how it is split up into colors by a prism.
is incorrect because a prism does not have all the colors of white light, but rather it separates the colors that are already present in white light.
is incorrect because total internal reflection occurs when light is completely reflected back into the same medium, which is not what happens when white light is split up by a prism.
Frage 11 Bericht
A lens of focal length 15cm forms on erect image which is three times the size of the object. The distance between the object and the image is ___.
Antwortdetails
We can use the lens formula, 1/f = 1/v - 1/u, where f is the focal length of the lens, v is the distance between the lens and the image, and u is the distance between the lens and the object.
From the problem, we know that the focal length of the lens is 15 cm, and the image is erect and three times the size of the object. This means that the image distance v is positive and the object distance u is negative (since the object is in front of the lens).
Let's assume that the object distance u is -x cm, where x is a positive number. Then, the image distance v is +3x cm, since the image is three times the size of the object. Substituting these values into the lens formula, we get:
1/15 = 1/(+3x) - 1/(-x)
Simplifying the right-hand side, we get:
1/15 = (1 + 3)/3x
Multiplying both sides by 3x, we get:
3x/15 = 4
Simplifying, we get:
x = 20
Therefore, the distance between the object and the lens is -20 cm (since it is in front of the lens), and the distance between the image and the lens is +60 cm (since it is behind the lens). The distance between the object and the image is the sum of these distances, which is:
(-20) + (+60) = 40 cm
Therefore, the answer is 40cm.
Frage 12 Bericht
Which of the following is the dimension of pressure
Antwortdetails
The dimension of pressure is ML-1T-2 Pressure is defined as the force per unit area. This means that pressure is dependent on the force applied and the area over which it is applied. The unit of force is measured in Newtons (N), and the unit of area is measured in square meters (m2). Therefore, the unit of pressure is N/m2, which is also known as Pascals (Pa). To determine the dimension of pressure, we need to break down the units into their fundamental dimensions of mass (M), length (L), and time (T). Force is measured in N, which is kg m/s2. Area is measured in m2, which is L2. Therefore, the dimension of pressure can be calculated as (kg m/s2)/(L2), which simplifies to ML-1T-2.
Frage 13 Bericht
A room is heated by means of a charcoal fire, an occupants of the room standing away from the fire is warmed mainly by
Antwortdetails
The main way that the occupants of a room standing away from a charcoal fire are warmed is by radiation. Radiation is the transfer of heat energy through electromagnetic waves, and it can travel through empty space.
In this scenario, the charcoal fire emits radiation in the form of infrared waves, which travel through the air and warm up the objects (including the occupants) in the room. Convection, on the other hand, is the transfer of heat through the movement of fluids (such as air), but in this case, the air in the room is not being actively circulated by a fan or other mechanism. Conduction involves the transfer of heat through direct contact between two objects, but the occupants are not in direct contact with the fire. Reflection refers to the bouncing of radiation off a surface, but it is not a significant factor in this scenario as most of the radiation is absorbed by the objects in the room.
Frage 14 Bericht
In a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are 30V and 40V respectively. What is the voltage across the capacitor?
Antwortdetails
Frage 15 Bericht
The product of force and time is?
Antwortdetails
The product of force and time is known as impulse.
Impulse can be defined as the change in momentum that an object experiences as a result of a force being applied to it over a period of time. In simpler terms, impulse is the "push" that an object receives from a force acting on it for a certain amount of time. The more force applied, or the longer the time the force is applied, the greater the impulse and the greater the change in momentum of the object.
It's important to note that impulse is a vector quantity, meaning it has both magnitude and direction. Impulse is a measure of the ability of a force to cause an object to change its velocity, and can be used to explain many phenomena in physics, such as why a heavy object is harder to stop than a lighter one, or why a soccer ball changes direction when it is kicked.
Frage 16 Bericht
A positively charged rod X is brought near an uncharged metal sphere Y and is then touched by a finger with X still in place. When the finger is removed, the result is that Y has
Antwortdetails
Frage 17 Bericht
Which of the following instruments is most suitable for measuring the outside diameter of a narrow pipe in a few millimeters in diameter?
Antwortdetails
The most suitable instrument for measuring the outside diameter of a narrow pipe in a few millimeters in diameter is a micrometer screw gauge.
A micrometer screw gauge is a precision measuring instrument that can accurately measure small dimensions with high accuracy. It has a spindle that moves towards an anvil and a scale that indicates the measurement. The spindle moves in response to a small rotation of the thimble, allowing for precise and sensitive measurements.
In contrast, a pair of calipers or a meter rule may not be accurate enough for measuring such small dimensions, and a tape rule may not be able to fit inside the narrow pipe. Therefore, a micrometer screw gauge is the most suitable option for measuring the outside diameter of a narrow pipe in a few millimeters in diameter.
Frage 18 Bericht
The amount of heat needed to raise the temperature of 10kg of Copper by 1K is its
Antwortdetails
The correct answer is "specific heat capacity."
Specific heat capacity is a measure of how much heat energy is required to raise the temperature of a certain amount of a substance by 1 degree Celsius (or 1 Kelvin, which is the same size as 1 degree Celsius).
In this case, we are dealing with 10kg of copper, so we need to know the specific heat capacity of copper. The specific heat capacity of copper is 0.385 J/g°C (joules per gram per degree Celsius).
To calculate the amount of heat needed to raise the temperature of 10kg of copper by 1K, we need to know the total mass of copper (10kg) and the specific heat capacity of copper (0.385 J/g°C).
The formula for calculating the amount of heat energy required is:
Heat energy = mass x specific heat capacity x change in temperature
Since we want to raise the temperature by 1K, the change in temperature is 1K.
So, the amount of heat energy required to raise the temperature of 10kg of copper by 1K is:
Heat energy = 10kg x 0.385 J/g°C x 1K = 3.85 kJ
Therefore, it takes 3.85 kilojoules (kJ) of heat energy to raise the temperature of 10kg of copper by 1K.
Frage 19 Bericht
What effort will a machine of efficiency 90% apply to a load of 180N if its efforts arm is twice as long as its load arm?
Antwortdetails
Frage 20 Bericht
Calculate the effective capacitance of the circuit in the diagram given
Antwortdetails
The three 2uf capacitors are in parallel to each other so u add them like this
2uf+2uf+2uf=6uf
So u have three capacitors in series
6uf 2uf and 3uf
They are in series so
1/C= 1/6+1/3=1/2
C=2uf
Then the same thing with the last two capay
1/2+1/2=1uf
Thanks
2uf+2uf+2uf=6uf
So u have three capacitors in series
6uf 2uf and 3uf
They are in series so
1/C= 1/6+1/3=1/2
C=2uf
Then the same thing with the last two capay
1/2+1/2=1uf
Thanks
Frage 21 Bericht
The differences observed in solids, liquids and gases may be accounted for by
Antwortdetails
The differences observed in solids, liquids, and gases can be accounted for by the spacing and forces acting between the molecules.
In a solid, the molecules are packed closely together, so they have a fixed shape and volume. The intermolecular forces are strong enough to keep the molecules in a fixed position relative to one another.
In a liquid, the molecules are still close together, but they are free to move around each other. The intermolecular forces are weaker than in a solid, so the molecules can slide past one another, giving the liquid its ability to flow and take the shape of its container.
In a gas, the molecules are widely spaced and are in constant motion. The intermolecular forces are very weak, so the molecules are free to move around and fill any available space. Gases have no fixed shape or volume.
So, the differences observed in solids, liquids, and gases can be explained by the spacing and forces acting between the molecules. It's not about their relative masses, melting points, or the different molecules in each of them.
Frage 22 Bericht
Water of mass 150g at \(60^\circ\)c is added to 300g of water at \(20^\circ\)c and the mixture is well stirred. Calculate the temperature of the mixture.(neglect heat losses to the surroundings)
Antwortdetails
To solve this problem, we can use the principle of conservation of energy, which states that energy cannot be created or destroyed, only transferred or converted from one form to another. In this case, the energy transferred is in the form of heat.
We can use the formula:
Q = m*c*(ΔT)
where Q is the heat transferred, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature.
First, we can calculate the heat transferred from the hot water to the cold water:
Q1 = 150g * 4.18 J/(g°C) * (60°C - T)
Q1 = 627 * (60 - T)
where T is the temperature of the mixture.
Next, we can calculate the heat transferred from the cold water to reach the final temperature of the mixture:
Q2 = 300g * 4.18 J/(g°C) * (T - 20°C)
Q2 = 1254 * (T - 20)
Since the heat transferred between the two water samples must be equal, we can set Q1 equal to Q2 and solve for T:
627 * (60 - T) = 1254 * (T - 20)
37620 - 627T = 1254T - 25080
1881T = 62760
T = 33.4°C
Therefore, the temperature of the mixture is approximately 33°C.
Answer: 33°C
Frage 23 Bericht
To keep a vehicle moving at a constant speed V requires power P from the engine. The force provided by the engine is
Antwortdetails
The force provided by the engine to keep a vehicle moving at a constant speed is proportional to the power (P) required from the engine. This power is proportional to the product of the speed (V) and force (P), so the relationship can be expressed as P = kV, where k is a proportionality constant.
Frage 24 Bericht
The pitch of an acoustic device can be increased by
Antwortdetails
The pitch of an acoustic device refers to the perceived highness or lowness of a sound, and is determined by the frequency of the sound wave. To increase the pitch of an acoustic device, you need to increase the frequency of the sound wave. This can be done by increasing the number of vibrations per second that the device produces.
So, the correct answer is to "increase the frequency".
Frage 25 Bericht
Palm oil from a bottle flows out more easily after it has been heated because the
Antwortdetails
Molecules cannot be given energy during the heating and the molecules of oil cannot force each other out
Frage 26 Bericht
An object is placed 20cm from a concave mirror of focal length 10cm. The linear magnification of the image produced is?
Antwortdetails
The linear magnification of an image is given by the formula:
magnification = height of image / height of object = -v/u
where v is the image distance, u is the object distance, and the negative sign indicates that the image is inverted.
In this problem, the object is placed 20cm from a concave mirror of focal length 10cm. Since the object is placed beyond the focal point, the image will be real and inverted.
Using the mirror formula 1/f = 1/v + 1/u, we can find the image distance v:
1/10 = 1/v + 1/20
Solving for v, we get:
v = -20 cm
Now, we can use the magnification formula to find the linear magnification:
magnification = -v/u = -(-20)/20 = 1
Therefore, the linear magnification of the image produced is 1, which means the image is the same size as the object and is also inverted.
The answer is: 1.
Frage 27 Bericht
Convex mirrors are used as driving mirrors because images formed are
Antwortdetails
Convex mirrors are used as driving mirrors because the images formed by them are "erect, virtual, and diminished."
Let me explain what these terms mean:
- Erect: It means that the image appears upright, just like the actual object. This is important for a driving mirror because it allows the driver to perceive the correct orientation of the vehicles behind them.
- Virtual: It means that the image appears to be behind the mirror, and not in front of it. This is also important for a driving mirror because it allows the driver to see a wider field of view without having to turn their head.
- Diminished: It means that the image is smaller than the actual object. This is important for a driving mirror because it allows the driver to see a larger area behind them while still fitting it within the mirror's frame.
Overall, these properties make convex mirrors ideal for use as driving mirrors as they provide the driver with an accurate view of the vehicles behind them without sacrificing their field of view.
Frage 28 Bericht
If the fraction of the atoms of a radioactive material left after 120years is \( \frac{1}{64} \), what is the half-life of the material? \( \frac{1}{64} \)
Antwortdetails
The half-life of a radioactive material is the time it takes for half of the atoms in a sample to decay. The fraction of atoms left after a certain number of half-lives can be calculated using the formula:
fraction left = (1/2)^(number of half-lives)
Let's use this formula to solve the problem. We know that the fraction of atoms left after 120 years is 1/64, which means that:
(1/2)^(number of half-lives) = 1/64
To solve for the number of half-lives, we can take the logarithm of both sides:
log[(1/2)^(number of half-lives)] = log(1/64)
Using the rule that log(a^b) = b*log(a), we can simplify the left side of the equation:
number of half-lives * log(1/2) = log(1/64)
Dividing both sides by log(1/2), we get:
number of half-lives = log(1/64) / log(1/2)
Using a calculator or the change of base formula, we can evaluate this expression:
number of half-lives = 6
Therefore, the half-life of the material is 120/6 = 20 years.
Frage 29 Bericht
The inner diameter of a small test tube can be measured accurately using a
Antwortdetails
A vernier caliper is a measuring device used to precisely measure linear dimensions. It is a very useful tool to use when measuring the diameter of a round objects like cylinders because the measuring jaws can be secured on either side of the circumference.
Vernier calipers have both a fixed main scale and a moving vernier scale. The main scale is graduated in either millimetres or tenths of an inch. The vernier scale allows much more precise readings to be taken (usually to the nearest 0.02mm or 0.001 inch) in comparison to a standard ruler (which only measures to th nearest 1mm or 0.25 inch).
The vernier scale was invented by French mathematician Pierre Vernier in 1631. As part of the vernier caliper, it is used together with the main scale, and helps to provide very precise measurements. Vernier calipers usually show either imperial or metric measurements, but some measure in both.
Vernier calipers have both a fixed main scale and a moving vernier scale. The main scale is graduated in either millimetres or tenths of an inch. The vernier scale allows much more precise readings to be taken (usually to the nearest 0.02mm or 0.001 inch) in comparison to a standard ruler (which only measures to th nearest 1mm or 0.25 inch).
The vernier scale was invented by French mathematician Pierre Vernier in 1631. As part of the vernier caliper, it is used together with the main scale, and helps to provide very precise measurements. Vernier calipers usually show either imperial or metric measurements, but some measure in both.
Frage 30 Bericht
A solid cube of side 50cm and mass 75kg floats in a liquid with \( \frac{1}{3} \) of its height above the liquid surface. The relative density of the liquid is?
Antwortdetails
Volume of liquid displaced
= 23 (0.5)3
Mass of liquid displaced = mass of floating cube = 75kg
Density of liquid = massvolume
= 75(73(0.5)) × 3
= 0.9 × 103kgm−3
R.D of liquid = (0.9)(1.0) × 103
= 0.9
= 23 (0.5)3
Mass of liquid displaced = mass of floating cube = 75kg
Density of liquid = massvolume
= 75(73(0.5)) × 3
= 0.9 × 103kgm−3
R.D of liquid = (0.9)(1.0) × 103
= 0.9
Frage 31 Bericht
A ball of mass 5.0kg hits a smooth vertical wall normally with a speed of \(2\text{ms}^{-1}\). Determine the magnitude of the resulting impulse
Antwortdetails
The magnitude of the resulting impulse can be calculated using the formula impulse = change in momentum. In this scenario, the ball experiences a change in velocity (speed) as it hits the wall. The ball's initial momentum is equal to its mass times its velocity, and its final momentum is zero since it comes to a stop after hitting the wall. The change in momentum is equal to the final momentum minus the initial momentum, which is equal to the negative of the initial momentum.
Since the ball has a mass of 5.0 kg and a velocity of 2 m/s, its initial momentum is 5.0 kg * 2 m/s = 10.0 kg m/s. Therefore, the change in momentum is -10.0 kg m/s and the magnitude of the resulting impulse is 10.0 kg m/s, which is equal to 10.0 Ns.
So, the correct answer is 10.0kgms−1.
Frage 32 Bericht
The electrochemical equivalent of silver is 0.0012g/C. If 36.0g of silver is to be deposited by electrolysis on a surface by passing a steady current for 5mins, the current must be?
Antwortdetails
The electrochemical equivalent of silver is a measure of the amount of silver that is deposited on a surface per unit of charge. In this case, the electrochemical equivalent of silver is 0.0012 grams per Coulomb of charge. To deposit 36.0 grams of silver by electrolysis, we need to know the amount of charge that must be passed through the solution.
The amount of charge is given by:
Q = m/z
where m is the mass of silver to be deposited, 0.0012 is the electrochemical equivalent of silver, and z is the charge on one mole of electrons (z = 1 for a single electron).
So, the amount of charge required is:
Q = 36.0 g / 0.0012 g/C = 30000 C
The current, I, is given by:
I = Q / t
where t is the time for which the current is flowing. In this case, t = 5 minutes.
So, the current required is:
I = 30000 C / (5 x 60 s) = 100 A
Therefore, the current must be 100 Amperes.
Frage 33 Bericht
A 20kg mass is to be pulled up a slope inclined at 300 to the horizontal. If efficiency of the plane is 75%. The force required to pull the load up the plane is J [g=10ms\(^{-2}\)]
Antwortdetails
The force required to pull a 20kg mass up a slope inclined at 300 can be calculated using the formula:
force = mass * gravity * sin(angle)
where mass is 20kg, gravity is 10 m/s^2 and angle is 300.
The formula for efficiency is:
efficiency = output force / input force
where output force is the force required to pull the mass up the slope and input force is the force applied to the rope.
Since the efficiency of the plane is 75%, the input force is 4 times the output force.
So, the output force can be calculated as:
output force = input force / 4
input force = mass * gravity * sin(angle) / efficiency
input force = 20 * 10 * sin(300) / 0.75
input force = 533.2 N
And the output force can be calculated as:
output force = input force / 4
output force = 533.2 / 4
output force = 133.3 N
So, the force required to pull the load up the plane is 133.3 N.
Frage 34 Bericht
An object weighs 30N in air and 21N in water. The weight of the object when completely immersed in a liquid of relative density 1.4 is
Antwortdetails
Weight of water displaced = upthrust = 30 - 21 = 9N
Mass of water displaced = 910
= 0.9kg
Volume of object = 9 × 10−4
m3
= (9 × 10−4
) (1.4 ×103)
= 1.26kg = 12N
30 - 12.6 = 17.4N
Frage 35 Bericht
Which of the following diagrams represents correctly an n-p-n transistor?
i.
ii
iii
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Frage 36 Bericht
A pulley system has three pulleys in the fixed block and two in the movable block and if the pulley has an efficiency of 72%, the mechanical advantage of the system is?
Antwortdetails
To make it easier understood
MA = E × Vr/100
Vr in a pulley system is the number of pulleys and in this case we have 5 (3 and 2)
So
MA = 72 × 5 = 360/100 = 3.6
Thanks
MA = E × Vr/100
Vr in a pulley system is the number of pulleys and in this case we have 5 (3 and 2)
So
MA = 72 × 5 = 360/100 = 3.6
Thanks
Frage 37 Bericht
Which of the following phenomena is the practical evidence for the existence of the continual motion of molecules.
Antwortdetails
Brownian motion is the practical evidence for the existence of the continual motion of molecules. This phenomenon is observed as the random movement of particles suspended in a fluid, such as a liquid or a gas, due to the constant bombardment of the fluid molecules. It was first described by the Scottish botanist Robert Brown in 1827 and provides strong evidence for the kinetic theory of matter, which states that all matter is made up of constantly moving particles. The random movement of the suspended particles can be observed through a microscope and is a direct result of the continual motion of the fluid molecules.
Frage 38 Bericht
Electrical power is transmitted at a high voltage rather than a low voltage because the amount of energy loss is due to
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The primary reason that power is transmitted at high voltages is to increase efficiency. As electricity is transmitted over long distances, there are inherent energy losses along the way. High voltage transmission minimizes the amount of power lost as electricity flows from one location to the next. How? The higher the voltage, the lower the current. The lower the current, the lower the resistance losses in the conductors. And when resistance losses are low, energy losses are low also. Electrical engineers consider factors such as the power being transmitted and the distance required for transmission when determining the optimal transmission voltage
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In the diagram given if the atmospheric pressure is 760mm, the pressure in the chamber G Is
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In the diagram shown, If the south-poles of two magnets stroke a steel bar, the polarities at T and V will respectively be
