Work, Energy & Power
Q. A 5 kg object is dropped from a height of 20 m. What is the potential energy at the top? (g = 9.8 m/s²)
A.
980 J
B.
490 J
C.
196 J
D.
9800 J
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Solution
Potential energy is given by PE = mgh. Here, PE = 5 * 9.8 * 20 = 980 J.
Correct Answer: A — 980 J
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Q. A 5 kg object is dropped from a height of 20 m. What is the total mechanical energy just before it hits the ground?
A.
0 J
B.
100 J
C.
200 J
D.
500 J
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Solution
Total mechanical energy is conserved. At height, PE = mgh = 5 * 9.8 * 20 = 980 J. Just before hitting the ground, total energy = 980 J.
Correct Answer: C — 200 J
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Q. A 5 kg object is lifted to a height of 10 m. What is the gravitational potential energy gained?
A.
50 J
B.
100 J
C.
200 J
D.
500 J
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Solution
Potential Energy (PE) = m * g * h = 5 kg * 10 m/s^2 * 10 m = 500 J
Correct Answer: B — 100 J
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Q. A 5 kg object is lifted to a height of 10 m. What is the potential energy gained?
A.
50 J
B.
100 J
C.
200 J
D.
500 J
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Solution
Potential Energy (PE) = m * g * h = 5 kg * 9.8 m/s^2 * 10 m = 490 J (approx. 500 J)
Correct Answer: B — 100 J
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Q. A 5 kg object is lifted to a height of 10 m. What is the work done against gravity?
A.
50 J
B.
100 J
C.
150 J
D.
200 J
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Solution
Work done against gravity is W = mgh = 5 * 9.8 * 10 = 490 J.
Correct Answer: D — 200 J
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Q. A 5 kg object is lifted to a height of 3 m. What is the work done against gravity?
A.
15 J
B.
30 J
C.
45 J
D.
60 J
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Solution
Work done against gravity is W = mgh = 5 * 9.8 * 3 = 147 J.
Correct Answer: B — 30 J
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Q. A 5 kg object is moving with a velocity of 3 m/s. What is its kinetic energy?
A.
22.5 J
B.
30 J
C.
45 J
D.
60 J
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Solution
Kinetic Energy = 0.5 × mass × velocity² = 0.5 × 5 kg × (3 m/s)² = 22.5 J.
Correct Answer: A — 22.5 J
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Q. A 50 kg object is moving with a velocity of 10 m/s. What is its momentum?
A.
500 kg m/s
B.
1000 kg m/s
C.
1500 kg m/s
D.
2000 kg m/s
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Solution
Momentum = mass × velocity = 50 kg × 10 m/s = 500 kg m/s.
Correct Answer: B — 1000 kg m/s
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Q. A 50 kg object is pushed with a force of 200 N over a distance of 10 m. What is the work done? (2000)
A.
2000 J
B.
1000 J
C.
500 J
D.
3000 J
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Solution
Work Done = Force * Distance = 200 N * 10 m = 2000 J
Correct Answer: A — 2000 J
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Q. A ball is thrown vertically upwards with a speed of 15 m/s. What is the maximum height it reaches? (g = 9.8 m/s²)
A.
11.5 m
B.
15.0 m
C.
22.5 m
D.
30.0 m
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Solution
Using the formula h = v² / (2g), h = (15 m/s)² / (2 × 9.8 m/s²) = 11.5 m.
Correct Answer: A — 11.5 m
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Q. A ball is thrown vertically upwards with a speed of 30 m/s. What is the maximum height it reaches? (g = 9.8 m/s²)
A.
45.9 m
B.
46.0 m
C.
46.1 m
D.
46.2 m
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Solution
Using conservation of energy, initial kinetic energy = potential energy at maximum height. 0.5mv² = mgh. Solving gives h = v²/(2g) = (30)²/(2 * 9.8) = 45.9 m.
Correct Answer: B — 46.0 m
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Q. A block of mass 2 kg is pushed along a frictionless surface by a constant force of 10 N. What is the work done by the force when the block moves 5 m?
A.
10 J
B.
20 J
C.
30 J
D.
50 J
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Solution
Work done = Force × Distance = 10 N × 5 m = 50 J.
Correct Answer: B — 20 J
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Q. A block of mass 2 kg is pushed along a frictionless surface by a force of 10 N. What is the work done by the force when the block moves 5 m?
A.
10 J
B.
20 J
C.
30 J
D.
50 J
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Solution
Work done = Force × Distance = 10 N × 5 m = 50 J.
Correct Answer: B — 20 J
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Q. A block of mass 2 kg is pushed along a horizontal surface with a constant force of 10 N. What is the work done by the force after moving the block 5 m?
A.
10 J
B.
20 J
C.
30 J
D.
50 J
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Solution
Work done = Force × Distance = 10 N × 5 m = 50 J.
Correct Answer: B — 20 J
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Q. A block of mass 2 kg is pushed along a horizontal surface with a force of 10 N. If the block moves a distance of 5 m, what is the work done on the block?
A.
10 J
B.
20 J
C.
30 J
D.
50 J
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Solution
Work done = Force × Distance = 10 N × 5 m = 50 J.
Correct Answer: B — 20 J
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Q. A block of mass 2 kg is pushed along a horizontal surface with a force of 10 N. If the block moves 5 m, what is the work done on the block?
A.
10 J
B.
20 J
C.
30 J
D.
50 J
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Solution
Work done = Force × Distance = 10 N × 5 m = 50 J.
Correct Answer: B — 20 J
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Q. A block of mass 2 kg is pushed along a horizontal surface with a force of 10 N. If the block moves 5 m, what is the work done by the force?
A.
10 J
B.
20 J
C.
30 J
D.
50 J
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Solution
Work done = Force × Distance = 10 N × 5 m = 50 J.
Correct Answer: B — 20 J
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Q. A block of mass 2 kg is pushed along a horizontal surface with a force of 10 N. If the block moves a distance of 5 m, what is the work done by the force?
A.
10 J
B.
20 J
C.
30 J
D.
50 J
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Solution
Work done = Force × Distance = 10 N × 5 m = 50 J.
Correct Answer: B — 20 J
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Q. A block of mass 2 kg is released from a height of 10 m. What is its speed just before it hits the ground? (g = 9.8 m/s²)
A.
14 m/s
B.
20 m/s
C.
10 m/s
D.
5 m/s
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Solution
Using conservation of energy, potential energy at height = kinetic energy just before hitting the ground. mgh = 0.5mv². Solving gives v = sqrt(2gh) = sqrt(2 * 9.8 * 10) = 14 m/s.
Correct Answer: A — 14 m/s
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Q. A block of mass 2 kg is released from a height of 10 m. What is its speed just before it hits the ground?
A.
0 m/s
B.
10 m/s
C.
14 m/s
D.
20 m/s
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Solution
Using conservation of energy, potential energy at height = kinetic energy just before hitting the ground. mgh = 0.5mv^2. Solving gives v = sqrt(2gh) = sqrt(2*9.8*10) = 14 m/s.
Correct Answer: C — 14 m/s
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Q. A block of mass 2 kg is released from a height of 5 m. What is its speed just before it hits the ground? (g = 9.8 m/s²)
A.
5 m/s
B.
10 m/s
C.
15 m/s
D.
20 m/s
Show solution
Solution
Using conservation of energy, potential energy at height = kinetic energy just before hitting the ground. mgh = 0.5mv². Solving gives v = √(2gh) = √(2 * 9.8 * 5) = 10 m/s.
Correct Answer: B — 10 m/s
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Q. A body of mass 2 kg is moving with a velocity of 3 m/s. What is its kinetic energy?
A.
9 J
B.
6 J
C.
18 J
D.
12 J
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Solution
Kinetic Energy (KE) = 1/2 * m * v^2 = 1/2 * 2 * (3^2) = 9 J
Correct Answer: A — 9 J
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Q. A car accelerates from rest to a speed of 20 m/s. If its mass is 1000 kg, what is the work done by the engine?
A.
200,000 J
B.
100,000 J
C.
50,000 J
D.
400,000 J
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Solution
Work Done = Change in Kinetic Energy = 1/2 * m * (v^2) = 1/2 * 1000 * (20^2) = 200,000 J
Correct Answer: A — 200,000 J
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Q. A car accelerates from rest to a speed of 20 m/s. If the mass of the car is 1000 kg, what is the work done by the engine?
A.
200,000 J
B.
100,000 J
C.
50,000 J
D.
400,000 J
Show solution
Solution
Work Done = Change in Kinetic Energy = 1/2 * m * (v^2) = 1/2 * 1000 * (20^2) = 200,000 J
Correct Answer: A — 200,000 J
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Q. A car accelerates from rest to a speed of 30 m/s. If the mass of the car is 800 kg, what is the work done on the car?
A.
360,000 J
B.
480,000 J
C.
600,000 J
D.
720,000 J
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Solution
Work done = Change in Kinetic Energy = 0.5 × mass × (final speed² - initial speed²) = 0.5 × 800 kg × (30 m/s)² = 360,000 J.
Correct Answer: B — 480,000 J
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Q. A car engine does 3000 J of work in 5 seconds. What is the average power output of the engine?
A.
600 W
B.
800 W
C.
1000 W
D.
1200 W
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Solution
Using the formula P = W/t, we find P = 3000 J / 5 s = 600 W.
Correct Answer: C — 1000 W
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Q. A car engine does 3000 J of work in 5 seconds. What is the power of the engine?
A.
600 W
B.
800 W
C.
1000 W
D.
1200 W
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Solution
Using the formula P = W/t, we have P = 3000 J / 5 s = 600 W.
Correct Answer: A — 600 W
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Q. A car of mass 1000 kg accelerates from rest to a speed of 20 m/s. What is the work done on the car?
A.
20000 J
B.
40000 J
C.
80000 J
D.
100000 J
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Solution
Kinetic energy = 0.5 × m × v^2 = 0.5 × 1000 kg × (20 m/s)^2 = 200000 J.
Correct Answer: B — 40000 J
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Q. A car of mass 1000 kg accelerates from rest to a speed of 20 m/s. What is the work done by the engine? (2000)
A.
20000 J
B.
40000 J
C.
50000 J
D.
80000 J
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Solution
Kinetic Energy = 0.5 × mass × velocity^2 = 0.5 × 1000 kg × (20 m/s)^2 = 200000 J.
Correct Answer: B — 40000 J
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Q. A car of mass 1000 kg is moving at a speed of 20 m/s. What is its kinetic energy?
A.
200 J
B.
400 J
C.
200,000 J
D.
400,000 J
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Solution
Kinetic energy is given by KE = 0.5mv². Here, KE = 0.5 * 1000 * (20)² = 200,000 J.
Correct Answer: C — 200,000 J
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