The Most Comprehensive Question Bank for ICSE Class 10 Students
Multiple Choice Questions (MCQs)
Question 1:
What is the work done by a force of 10 N moving an object through a distance of 5 m along the direction of the force?
a) 2 J
b) 15 J
c) 50 J
d) 500 J
Solution:
Correct Answer: c) 50 J
Explanation:
Work done is calculated as the product of force and displacement in the direction of the force. Here, Work = Force × Distance = 10 N × 5 m = 50 J.
Question 2:
What is the gravitational potential energy of an object of mass 2 kg placed at a height of 5 meters? (Assume g = 10 m/s²)
a) 10 J
b) 20 J
c) 100 J
d) 200 J
Solution:
Correct Answer: c) 100 J
Explanation:
Gravitational potential energy is given by the formula P.E. = mgh. Substituting the given values, P.E. = 2 kg × 10 m/s² × 5 m = 100 J.
Question 3:
A car of mass 1000 kg is moving with a velocity of 10 m/s. What is its kinetic energy?
a) 50000 J
b) 100000 J
c) 5000 J
d) 10000 J
Solution:
Correct Answer: b) 100000 J
Explanation:
Kinetic energy (K.E.) = 1/2 mv². Substituting the given values, K.E. = 1/2 × 1000 kg × (10 m/s)² = 100000 J.
Question 4:
How much power is expended if 2000 J of work is done in 10 seconds?
a) 200 W
b) 20 W
c) 2000 W
d) 0.2 W
Solution:
Correct Answer: a) 200 W
Explanation:
Power is work done per unit time. Power = Work / Time = 2000 J / 10 s = 200 W.
Question 5:
Which unit is equivalent to a Newton-meter?
a) Joule
b) Pascal
c) Watt
d) Ampere
Solution:
Correct Answer: a) Joule
Explanation:
A Newton-meter is the SI unit of work or energy and is equivalent to a Joule.
Question 6:
What happens to the kinetic energy of a moving object if its velocity is doubled?
a) It remains the same.
b) It doubles.
c) It quadruples.
d) It halves.
Solution:
Correct Answer: c) It quadruples.
Explanation:
Kinetic energy is proportional to the square of velocity. If the velocity is doubled, kinetic energy becomes four times (2² = 4).
Question 7:
An object is lifted to a certain height. Which factor does not affect its potential energy?
a) Mass of the object
b) Height to which it is lifted
c) Acceleration due to gravity
d) Color of the object
Solution:
Correct Answer: d) Color of the object
Explanation:
Potential energy depends on mass, height, and gravity, not on properties like color.
Question 8:
A 500 W device is running for 4 hours. What is the total energy consumed?
a) 2000 Wh
b) 200 Wh
c) 2 kWh
d) 0.5 kWh
Solution:
Correct Answer: c) 2 kWh
Explanation:
Energy consumed = Power × Time = 500 W × 4 h = 2000 Wh = 2 kWh.
Question 9:
What is the unit of work in the CGS (Centimeter-Gram-Second) system?
a) Joule
b) Erg
c) Newton-meter
d) Watt
Solution:
Correct Answer: b) Erg
Explanation:
In the CGS system, the unit of work is the erg. One erg is defined as the work done by a force of one dyne exerted over one centimeter.
Question 10:
If a force acts perpendicular to the direction of displacement, what is the work done by the force?
a) Maximum possible work
b) Zero
c) Depends on the magnitude of the force
d) Cannot be determined
Solution:
Correct Answer: b) Zero
Explanation:
When the force is perpendicular to the displacement, the angle θ between force and displacement is 90°, and cos 90° = 0. Therefore, the work done, which is calculated as W = F × d × cosθ, is zero.
Question 11:
A 2 kg object is moving with a speed of 3 m/s. What is the kinetic energy of the object?
a) 9 J
b) 18 J
c) 6 J
d) 3 J
Solution:
Correct Answer: b) 18 J
Explanation:
Kinetic energy (K.E.) = 1/2 mv². Substituting the given values, K.E. = 1/2 × 2 kg × (3 m/s)² = 18 J.
Question 12:
Which of the following is a scalar quantity?
a) Velocity
b) Acceleration
c) Force
d) Work
Solution:
Correct Answer: d) Work
Explanation:
Work is a scalar quantity because it only has magnitude and no direction.
Question 13:
An object has a kinetic energy of 100 J and a mass of 25 kg. What is the speed of the object?
a) 2 m/s
b) 4 m/s
c) 8 m/s
d) 1 m/s
Solution:
Correct Answer: a) 2 m/s
Explanation:
Rearranging the kinetic energy formula K.E. = 1/2 mv² to solve for velocity: v = √(2K.E./m) = √(2 × 100 J / 25 kg) = 2 m/s.
Question 14:
How much energy is transferred if a force of 5 N moves an object 3 meters in the direction of the force?
a) 15 J
b) 8 J
c) 5 J
d) 1.5 J
Solution:
Correct Answer: a) 15 J
Explanation:
Work done, W = Force × Displacement. Here, W = 5 N × 3 m = 15 J.
Question 15:
What is the power output of a machine that does 500 J of work in 10 seconds?
a) 50 W
b) 5000 W
c) 5 W
d) 500 W
Solution:
Correct Answer: a) 50 W
Explanation:
Power = Work / Time. Therefore, Power = 500 J / 10 s = 50 W.
Question 16:
Which form of energy is stored in a stretched rubber band?
a) Kinetic energy
b) Thermal energy
c) Potential energy
d) Chemical energy
Solution:
Correct Answer: c) Potential energy
Explanation:
A stretched rubber band possesses elastic potential energy due to its position and the strain in the material.
Question 17:
What happens to the kinetic energy of a car if its mass is kept constant but its velocity is tripled?
a) It remains the same.
b) It triples.
c) It increases nine times.
d) It doubles.
Solution:
Correct Answer: c) It increases nine times.
Explanation:
Kinetic energy (K.E.) = 1/2 mv². If the velocity is tripled and mass remains constant, the kinetic energy increases by a factor of 3² (since K.E. ∝ v²), which is nine times.
Question 18:
A machine lifts a load of 200 kg to a height of 5 meters in 10 seconds. What is the power of the machine? (Assume g = 10 m/s²)
a) 1000 W
b) 100 W
c) 10 W
d) 10000 W
Solution:
Correct Answer: a) 1000 W
Explanation:
The work done is given by W = mgh = 200 kg × 10 m/s² × 5 m = 10000 J. Power = Work/Time = 10000 J / 10 s = 1000 W.
Question 19:
What is the main energy transformation in a loudspeaker?
a) Mechanical to Electrical
b) Electrical to Sound
c) Chemical to Electrical
d) Sound to Mechanical
Solution:
Correct Answer: b) Electrical to Sound
Explanation:
In a loudspeaker, electrical energy is converted into sound energy.
Question 20:
If the displacement of an object is perpendicular to the direction of the applied force, the work done is:
a) Positive
b) Negative
c) Maximum
d) Zero
Solution:
Correct Answer: d) Zero
Explanation:
If the force is perpendicular to displacement, the angle between force and displacement is 90 degrees, and cos(90°) = 0. Therefore, work done, W = F × d × cos(90°) = 0.
Question 21:
What is the kinetic energy of a 10 kg object moving at a velocity of 2 m/s?
a) 40 J
b) 20 J
c) 10 J
d) 4 J
Solution:
Correct Answer: b) 20 J
Explanation:
Kinetic energy (K.E.) = 1/2 mv² = 1/2 × 10 kg × (2 m/s)² = 20 J.
Question 22:
Which of the following is not a form of potential energy?
a) Gravitational
b) Elastic
c) Nuclear
d) Kinetic
Solution:
Correct Answer: d) Kinetic
Explanation:
Kinetic energy is the energy of motion, not a form of potential energy.
Question 23:
A ball is thrown upwards with a velocity of 10 m/s. What is the maximum height it reaches? (Assume g = 10 m/s²)
a) 1 m
b) 5 m
c) 10 m
d) 20 m
Solution:
Correct Answer: b) 5 m
Explanation:
At maximum height, kinetic energy is zero. Using the equation of motion, v² = u² – 2gh, where v = 0, u = 10 m/s, and g = 10 m/s². Solving, h = 5 m.
Question 24:
What is the unit of energy in the SI system?
a) Erg
b) Watt
c) Joule
d) Newton
Solution:
Correct Answer: c) Joule
Explanation:
In the SI system, the unit of energy is the Joule.
Question 25:
Which of the following situations represents the conversion of kinetic energy into potential energy?
a) A car slowing down.
b) Water flowing from a higher to a lower level.
c) A ball being thrown upwards.
d) A battery powering a flashlight.
Solution:
Correct Answer: c) A ball being thrown upwards.
Explanation:
As a ball is thrown upwards, its kinetic energy (due to motion) gets converted into potential energy (due to height).
Question 26:
What is the energy possessed by an object due to its motion?
a) Potential Energy
b) Kinetic Energy
c) Chemical Energy
d) Thermal Energy
Solution:
Correct Answer: b) Kinetic Energy
Explanation:
Kinetic energy is the energy that an object possesses due to its motion.
Question 27:
A light and a heavy object have the same kinetic energy. Which one has a higher velocity?
a) The light object.
b) The heavy object.
c) Both have the same velocity.
d) Cannot be determined.
Solution:
Correct Answer: a) The light object.
Explanation:
Since kinetic energy (K.E.) = 1/2 mv², for the same K.E., a lighter object (smaller m) must have a higher velocity (v) compared to a heavier object.
Question 28:
Which of the following is a measure of how quickly work is done?
a) Energy
b) Power
c) Efficiency
d) Momentum
Solution:
Correct Answer: b) Power
Explanation:
Power is defined as the rate at which work is done or energy is transferred.
Question 29:
How much power is required to lift a 200 kg object to a height of 10 meters in 5 seconds? (Assume g = 10 m/s²)
a) 400 W
b) 2000 W
c) 4000 W
d) 1000 W
Solution:
Correct Answer: a) 400 W
Explanation:
Work done = mgh = 200 kg × 10 m/s² × 10 m = 20000 J. Power = Work / Time = 20000 J / 5 s = 4000 W.
Question 30:
If the speed of an object is halved, what happens to its kinetic energy?
a) It remains the same.
b) It is halved.
c) It is quartered.
d) It is doubled.
Solution:
Correct Answer: c) It is quartered.
Explanation:
Kinetic energy is proportional to the square of the velocity. If the speed is halved, the kinetic energy is reduced to one-fourth of its original value.
Question 31:
What type of energy is stored in food?
a) Kinetic Energy
b) Potential Energy
c) Chemical Energy
d) Mechanical Energy
Solution:
Correct Answer: c) Chemical Energy
Explanation:
Food stores energy in the form of chemical energy, which is released during digestion and metabolic processes.
Question 32:
In which of the following scenarios is work done?
a) Pushing against a stationary wall.
b) Holding a heavy box stationary.
c) Lifting a book from the floor to the table.
d) Carrying a bag while walking at a constant speed.
Solution:
Correct Answer: c) Lifting a book from the floor to the table.
Explanation:
Work is done when a force causes a displacement in the direction of the force. Lifting a book involves moving it against gravity, which constitutes work.
Question 33:
What is the potential energy of a 2 kg object placed at a height of 3 meters above the ground? (Assume g = 9.8 m/s²)
a) 58.8 J
b) 29.4 J
c) 5.88 J
d) 17.64 J
Solution:
Correct Answer: a) 58.8 J
Explanation:
Potential energy (P.E.) = mgh = 2 kg × 9.8 m/s² × 3 m = 58.8 J.
Question 34:
Which of the following is not a renewable energy source?
a) Solar energy
b) Wind energy
c) Coal
d) Hydropower
Solution:
Correct Answer: c) Coal
Explanation:
Coal is a fossil fuel and not a renewable energy source, unlike solar, wind, and hydropower.
Question 35:
What happens to the potential energy of an object when it falls freely towards the earth?
a) It increases.
b) It decreases.
c) It stays the same.
d) It first increases then decreases.
Solution:
Correct Answer: b) It decreases.
Explanation:
As an object falls, its height decreases, thereby reducing its gravitational potential energy.
Question 36:
A 100 W light bulb is used for 10 hours. How much energy does it consume?
a) 1 kWh
b) 10 kWh
c) 0.1 kWh
d) 1000 kWh
Solution:
Correct Answer: a) 1 kWh
Explanation:
Energy consumed = Power × Time = 100 W × 10 h = 1000 Wh = 1 kWh.
Question 37:
The energy transformation in a hydroelectric power plant is primarily from:
a) Chemical to Electrical
b) Electrical to Mechanical
c) Potential to Kinetic to Electrical
d) Solar to Electrical
Solution:
Correct Answer: c) Potential to Kinetic to Electrical
Explanation:
In a hydroelectric plant, water at a height has potential energy which gets converted to kinetic energy as it falls down and then to electrical energy through turbines.
Question 38:
What is the unit of force in the SI system?
a) Dyne
b) Newton
c) Joule
d) Watt
Solution:
Correct Answer: b) Newton
Explanation:
In the SI system, the unit of force is Newton.
Question 39:
An object is thrown vertically upwards with a velocity v. At its highest point, its velocity is:
a) 0
b) v
c) 2v
d) v/2
Solution:
Correct Answer: a) 0
Explanation:
At its highest point, the object momentarily stops before falling back, so its velocity is 0.
Question 40:
Which energy transformation occurs in a battery-operated toy car?
a) Chemical to Kinetic
b) Kinetic to Potential
c) Potential to Kinetic
d) Electrical to Chemical
Solution:
Correct Answer: a) Chemical to Kinetic
Explanation:
In a battery-operated toy car, the chemical energy stored in the battery is converted into kinetic energy of the moving car.
Question 41:
A person lifts a 20 kg crate to a height of 1 meter in 2 seconds. What is the power exerted? (Assume g = 10 m/s²)
a) 100 W
b) 200 W
c) 50 W
d) 10 W
Solution:
Correct Answer: a) 100 W
Explanation:
Work done = mgh = 20 kg × 10 m/s² × 1 m = 200 J. Power = Work / Time = 200 J / 2 s = 100 W.
Question 42:
What does 1 kilowatt-hour represent?
a) The energy used by a 1 kW appliance in 1 minute.
b) The energy used by a 1 kW appliance in 1 hour.
c) The power used by a 1 kW appliance in 1 hour.
d) The energy used by a 1 kW appliance in 1 second.
Solution:
Correct Answer: b) The energy used by a 1 kW appliance in 1 hour.
Explanation:
1 kilowatt-hour is the amount of energy used by an appliance of power 1 kilowatt over a period of 1 hour.
Question 43:
A force of 5 N causes a displacement of 2 m in the direction of the force. The work done is:
a) 2.5 J
b) 7 J
c) 10 J
d) 5 J
Solution:
Correct Answer: c) 10 J
Explanation:
Work done = Force × Displacement = 5 N × 2 m = 10 J.
Question 44:
Which type of energy transfer occurs when sunlight is converted into electricity by solar panels?
a) Mechanical to Electrical
b) Chemical to Electrical
c) Thermal to Electrical
d) Light to Electrical
Solution:
Correct Answer: d) Light to Electrical
Explanation:
Solar panels convert light energy (from the sun) directly into electrical energy.
Question 45:
A car of mass 1000 kg accelerates from 0 to 20 m/s in 10 seconds. What is the average power developed by the engine? (Neglect air resistance and friction)
a) 2000 W
b) 4000 W
c) 200 W
d) 400 W
Solution:
Correct Answer: a) 2000 W
Explanation:
Kinetic energy = 1/2 mv² = 1/2 × 1000 kg × (20 m/s)² = 200000 J. Power = Work / Time = 200000 J / 10 s = 20000 W.
Question 46:
Which of the following is true for an object in free fall?
a) Its potential energy increases, and kinetic energy decreases.
b) Its potential energy and kinetic energy both increase.
c) Its potential energy decreases, and kinetic energy increases.
d) Its potential energy and kinetic energy both decrease.
Solution:
Correct Answer: c) Its potential energy decreases, and kinetic energy increases.
Explanation:
As an object falls, its height decreases, reducing its potential energy, while its speed increases, raising its kinetic energy.
Question 47:
What is the main energy transformation in an electric fan?
a) Electrical to Mechanical
b) Mechanical to Electrical
c) Thermal to Mechanical
d) Chemical to Electrical
Solution:
Correct Answer: a) Electrical to Mechanical
Explanation:
An electric fan converts electrical energy into mechanical energy (motion).
Question 48:
If an object’s mass is 4 kg and its velocity is 3 m/s, what is its kinetic energy?
a) 18 J
b) 36 J
c) 12 J
d) 6 J
Solution:
Correct Answer: a) 18 J
Explanation:
Kinetic energy (K.E.) = 1/2 mv² = 1/2 × 4 kg × (3 m/s)² = 18 J.
Question 49:
The rate of doing work or the rate of transfer of energy is defined as:
a) Energy
b) Power
c) Force
d) Momentum
Solution:
Correct Answer: b) Power
Explanation:
Power is defined as the rate of doing work or the rate of transfer of energy.
Question 50:
An object of mass 10 kg is moving with a uniform velocity of 5 m/s. What is its kinetic energy?
a) 25 J
b) 125 J
c) 250 J
d) 50 J
Solution:
Correct Answer: c) 250 J
Explanation:
Kinetic energy (K.E.) = 1/2 mv² = 1/2 × 10 kg × (5 m/s)² = 250 J.
Question 51:
A machine does 600 J of work in 5 seconds. The power of the machine is:
a) 120 W
b) 3000 W
c) 30 W
d) 600 W
Solution:
Correct Answer: a) 120 W
Explanation:
Power = Work / Time = 600 J / 5 s = 120 W.
Question 52:
What happens to the kinetic energy of a body if its velocity is reduced to half of its original velocity?
a) It becomes half.
b) It becomes one-fourth.
c) It remains the same.
d) It becomes double.
Solution:
Correct Answer: b) It becomes one-fourth.
Explanation:
Kinetic energy is proportional to the square of the velocity. If the velocity is halved, kinetic energy becomes one-fourth of its original value.
Question 53:
The energy stored in a dam is:
a) Kinetic Energy
b) Potential Energy
c) Thermal Energy
d) Electrical Energy
Solution:
Correct Answer: b) Potential Energy
Explanation:
The water stored in a dam possesses potential energy due to its height.
Question 54:
A motor lifts a weight of 500 N to a height of 10 meters in 25 seconds. The power of the motor is:
a) 200 W
b) 20 W
c) 500 W
d) 50 W
Solution:
Correct Answer: a) 200 W
Explanation:
Work done = Force × Displacement = 500 N × 10 m = 5000 J. Power = Work / Time = 5000 J / 25 s = 200 W.
Question 55:
In which of the following scenarios is no work done?
a) Pushing a car up a hill.
b) Lifting a book off the floor.
c) Carrying a box while walking on a level road.
d) Pulling a sled on a snowy surface.
Solution:
Correct Answer: c) Carrying a box while walking on a level road.
Explanation:
If the force is perpendicular to the direction of motion (like carrying a box while walking horizontally), no work is done.
Question 56:
What is the primary energy transformation in a coal-fired power plant?
a) Chemical to Electrical
b) Mechanical to Electrical
c) Solar to Electrical
d) Nuclear to Electrical
Solution:
Correct Answer: a) Chemical to Electrical
Explanation:
In a coal-fired power plant, chemical energy stored in coal is converted into electrical energy.
Question 57:
What is the gravitational potential energy of a 1 kg object at a height of 10 meters above the ground? (Assume g = 9.8 m/s²)
a) 9.8 J
b) 98 J
c) 980 J
d) 10 J
Solution:
Correct Answer: b) 98 J
Explanation:
Gravitational potential energy (P.E.) = mgh = 1 kg × 9.8 m/s² × 10 m = 98 J.
Question 58:
Which of the following represents the conversion of potential energy to kinetic energy?
a) A parked car starting to move.
b) Water flowing from a higher elevation to a lower elevation.
c) Charging a battery.
d) Freezing water into ice.
Solution:
Correct Answer: b) Water flowing from a higher elevation to a lower elevation.
Explanation:
As water flows from a higher to a lower elevation, its potential energy is converted into kinetic energy.
Question 59:
A force acts on a body and displaces it. The work done is negative when:
a) The displacement is in the direction of the force.
b) The displacement is opposite to the direction of the force.
c) The force is perpendicular to the displacement.
d) No displacement occurs.
Solution:
Correct Answer: b) The displacement is opposite to the direction of the force.
Explanation:
Work is considered negative when the force and displacement are in opposite directions.
Question 60:
What unit is used to measure energy in food?
a) Joule
b) Calorie
c) Newton
d) Watt
Solution:
Correct Answer: b) Calorie
Explanation:
Energy in food is typically measured in Calories.
Question 61:
Which of the following is a renewable source of energy?
a) Petroleum
b) Coal
c) Natural Gas
d) Wind
Solution:
Correct Answer: d) Wind
Explanation:
Wind is a renewable source of energy, unlike fossil fuels like petroleum, coal, and natural gas.
Question 62:
If a 10 W bulb is used for 5 hours, how much energy does it consume?
a) 50 Wh
b) 500 Wh
c) 50 kWh
d) 500 kWh
Solution:
Correct Answer: a) 50 Wh
Explanation:
Energy consumed = Power × Time = 10 W × 5 h = 50 Wh.
Question 63:
In an electric heater, electrical energy is primarily converted into:
a) Mechanical energy
b) Light energy
c) Heat energy
d) Sound energy
Solution:
Correct Answer: c) Heat energy
Explanation:
An electric heater converts electrical energy into heat energy.
Question 64:
When a pendulum swings from one side to the other, which type of energy transformation occurs at the highest point?
a) Kinetic to Potential
b) Potential to Kinetic
c) Mechanical to Thermal
d) Electrical to Mechanical
Solution:
Correct Answer: b) Potential to Kinetic
Explanation:
At the highest point in its swing, a pendulum’s potential energy is being converted into kinetic energy.
Question 65:
An electric fan transforms electrical energy mainly into:
a) Chemical energy
b) Mechanical energy
c) Heat energy
d) Nuclear energy
Solution:
Correct Answer: b) Mechanical energy
Explanation:
An electric fan primarily converts electrical energy into mechanical energy, which is used to rotate the blades.
Question 66:
What is the work done by a force of 10 N moving an object through a distance of 4 m in the direction of the force?
a) 40 J
b) 14 J
c) 6 J
d) 2.5 J
Solution:
Correct Answer: a) 40 J
Explanation:
Work done = Force × Distance. Here, W = 10 N × 4 m = 40 J.
Question 67:
A car engine develops a power of 80 kW. What is this power in horsepower (hp)? (Note: 1 hp = 746 W)
a) About 107.24 hp
b) About 60 hp
c) About 80 hp
d) About 120 hp
Solution:
Correct Answer: a) About 107.24 hp
Explanation:
Power in hp = Power in watts / 746 W/hp. So, 80,000 W / 746 W/hp ≈ 107.24 hp.
Question 68:
Which of these energy sources is considered the most environmentally friendly?
a) Coal
b) Solar
c) Diesel
d) Natural Gas
Solution:
Correct Answer: b) Solar
Explanation:
Solar energy is considered the most environmentally friendly as it is clean and renewable, unlike fossil fuels like coal, diesel, and natural gas.
Question 69:
A ball of mass 2 kg is dropped from a height of 10 m. What is its potential energy at the top? (Assume g = 9.8 m/s²)
a) 196 J
b) 20 J
c) 98 J
d) 200 J
Solution:
Correct Answer: a) 196 J
Explanation:
Potential energy (P.E.) = mgh = 2 kg × 9.8 m/s² × 10 m = 196 J.
Question 70:
If a machine does 1000 J of work in 50 seconds, its power is:
a) 50 W
b) 20 W
c) 500 W
d) 2000 W
Solution:
Correct Answer: b) 20 W
Explanation:
Power = Work / Time = 1000 J / 50 s = 20 W.
Question 71:
The energy possessed by a body due to its position or configuration is known as:
a) Kinetic energy
b) Potential energy
c) Thermal energy
d) Electrical energy
Solution:
Correct Answer: b) Potential energy
Explanation:
Potential energy is the energy that a body possesses due to its position or configuration.
Question 72:
Which of the following is a unit of power?
a) Newton
b) Joule
c) Watt
d) Pascal
Solution:
Correct Answer: c) Watt
Explanation:
The Watt is the unit of power in the International System of Units (SI).
Question 73:
What is the work done when a force of 5 N displaces an object by 3 m in a direction perpendicular to the force?
a) 15 J
b) 0 J
c) 5 J
d) 3 J
Solution:
Correct Answer: b) 0 J
Explanation:
When force is perpendicular to displacement, the work done is zero.
Question 74:
What is the kinetic energy of a 3 kg object moving at a speed of 4 m/s?
a) 24 J
b) 48 J
c) 12 J
d) 6 J
Solution:
Correct Answer: a) 24 J
Explanation:
Kinetic energy (K.E.) = 1/2 mv² = 1/2 × 3 kg × (4 m/s)² = 24 J.
Question 75:
A crane lifts a 500 kg weight through a height of 20 m in 1 minute. What is the power of the crane? (Assume g = 10 m/s²)
a) 10000 W
b) 166.67 W
c) 1000 W
d) 200 W
Solution:
Correct Answer: b) 166.67 W
Explanation:
Work done = mgh = 500 kg × 10 m/s² × 20 m = 100000 J. Power = Work / Time = 100000 J / 60 s ≈ 166.67 W.
Question 76:
Which of the following energy conversions occurs in a battery?
a) Mechanical to Electrical
b) Electrical to Mechanical
c) Chemical to Electrical
d) Electrical to Chemical
Solution:
Correct Answer: c) Chemical to Electrical
Explanation:
In a battery, chemical energy is converted into electrical energy.
Question 77:
A ball is dropped from a height of 5 m. What will be its speed just before it hits the ground? (Ignore air resistance and assume g = 10 m/s²)
a) 10 m/s
b) 5 m/s
c) 25 m/s
d) 7.07 m/s
Solution:
Correct Answer: a) 10 m/s
Explanation:
Using the equation v² = u² + 2gh (where u = initial velocity = 0), v = √(2 × 10 m/s² × 5 m) = 10 m/s.
Question 78:
Which unit is used to measure the energy content of food?
a) Joule
b) Calorie
c) Watt
d) Newton
Solution:
Correct Answer: b) Calorie
Explanation:
The energy content of food is commonly measured in Calories.
Question 79:
An object of mass 2 kg moving at 2 m/s has its speed increased to 4 m/s. What is the change in its kinetic energy?
a) 12 J
b) 8 J
c) 16 J
d) 4 J
Solution:
Correct Answer: a) 12 J
Explanation:
Initial K.E. = 1/2 × 2 kg × (2 m/s)² = 4 J. Final K.E. = 1/2 × 2 kg × (4 m/s)² = 16 J. Change in K.E. = 16 J – 4 J = 12 J.
Question 80:
The energy conversion in a hydroelectric power plant is:
a) Chemical to Electrical
b) Potential to Kinetic to Electrical
c) Thermal to Mechanical to Electrical
d) Nuclear to Electrical
Solution:
Correct Answer: b) Potential to Kinetic to Electrical
Explanation:
In a hydroelectric power plant, water’s potential energy is first converted to kinetic energy and then to electrical energy.