Work, Energy & Power
Q. A 10 N force is applied to move an object 3 m. What is the work done if the force is applied at an angle of 60 degrees to the direction of motion?
-
A.
15 J
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B.
30 J
-
C.
25 J
-
D.
20 J
Solution
Work done = Force × Distance × cos(θ) = 10 N × 3 m × cos(60°) = 10 N × 3 m × 0.5 = 15 J
Correct Answer: A — 15 J
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Q. A 1000 kg car is moving at a speed of 15 m/s. What is its kinetic energy?
-
A.
112,500 J
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B.
75,000 J
-
C.
50,000 J
-
D.
25,000 J
Solution
Kinetic Energy = 0.5 * m * v² = 0.5 * 1000 kg * (15 m/s)² = 112,500 J.
Correct Answer: A — 112,500 J
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Q. A 15 kg object is lifted to a height of 4 m. What is the work done against gravity? (g = 9.8 m/s²) (2021)
-
A.
588 J
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B.
5880 J
-
C.
392 J
-
D.
294 J
Solution
Work = mgh = 15 kg * 9.8 m/s² * 4 m = 588 J.
Correct Answer: A — 588 J
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Q. A 2 kg object is lifted to a height of 5 m. What is the potential energy gained by the object? (2022)
-
A.
10 J
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B.
20 J
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C.
30 J
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D.
40 J
Solution
Potential Energy = mass × g × height = 2 kg × 10 m/s² × 5 m = 100 J
Correct Answer: B — 20 J
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Q. A 2 kg object is lifted to a height of 5 m. What is the potential energy gained by the object? (g = 9.8 m/s²)
-
A.
98 J
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B.
19.6 J
-
C.
39.2 J
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D.
49 J
Solution
Potential Energy = mass × g × height = 2 kg × 9.8 m/s² × 5 m = 98 J
Correct Answer: A — 98 J
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Q. A 3 kg object is dropped from a height of 10 m. What is the potential energy at the top? (2022)
-
A.
30 J
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B.
60 J
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C.
90 J
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D.
120 J
Solution
Potential Energy = mass × g × height = 3 kg × 10 m/s² × 10 m = 300 J
Correct Answer: C — 90 J
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Q. A 4 kg object is lifted to a height of 2 m. What is the work done against gravity? (2022)
-
A.
40 J
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B.
80 J
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C.
20 J
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D.
60 J
Solution
Work done = mass × g × height = 4 kg × 10 m/s² × 2 m = 80 J
Correct Answer: B — 80 J
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Q. A 5 kg object is dropped from a height of 10 m. What is its potential energy at the top? (g = 9.8 m/s²)
-
A.
490 J
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B.
98 J
-
C.
50 J
-
D.
100 J
Solution
Potential Energy = mgh = 5 kg * 9.8 m/s² * 10 m = 490 J.
Correct Answer: A — 490 J
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Q. A 5 kg object is dropped 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
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B.
20 m/s
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C.
10 m/s
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D.
15 m/s
Solution
Using energy conservation, Potential Energy = Kinetic Energy at the ground: mgh = 0.5mv²; v = √(2gh) = √(2 × 9.8 m/s² × 10 m) = 14 m/s
Correct Answer: A — 14 m/s
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Q. A car of mass 1000 kg accelerates from rest to a speed of 20 m/s. What is the kinetic energy gained?
-
A.
200,000 J
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B.
100,000 J
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C.
50,000 J
-
D.
20,000 J
Solution
Kinetic Energy = 0.5 * m * v² = 0.5 * 1000 kg * (20 m/s)² = 200,000 J.
Correct Answer: B — 100,000 J
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Q. A cyclist does 1500 J of work to climb a hill. If he takes 5 minutes, what is his average power output?
-
A.
5 W
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B.
10 W
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C.
15 W
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D.
20 W
Solution
Power = Work / Time = 1500 J / (5 * 60 s) = 5 W.
Correct Answer: B — 10 W
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Q. A cyclist does 600 J of work to climb a hill. If he takes 30 seconds, what is his average power output? (2022)
-
A.
10 W
-
B.
20 W
-
C.
30 W
-
D.
40 W
Solution
Power = Work / Time = 600 J / 30 s = 20 W.
Correct Answer: B — 20 W
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Q. A force of 10 N is applied to move a box 5 m across a floor. What is the work done on the box?
-
A.
10 J
-
B.
20 J
-
C.
50 J
-
D.
5 J
Solution
Work done = Force × Distance = 10 N × 5 m = 50 J
Correct Answer: B — 20 J
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Q. A force of 10 N is applied to move a box 5 m along a horizontal surface. What is the work done by the force? (2021)
-
A.
20 J
-
B.
50 J
-
C.
10 J
-
D.
5 J
Solution
Work done = Force × Distance = 10 N × 5 m = 50 J
Correct Answer: B — 50 J
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Q. A force of 50 N is applied to move an object 4 m. How much work is done?
-
A.
100 J
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B.
150 J
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C.
200 J
-
D.
250 J
Solution
Work = Force * Distance = 50 N * 4 m = 200 J.
Correct Answer: C — 200 J
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Q. A machine does 1200 J of work in 60 seconds. What is its efficiency if the input energy is 2000 J? (2022)
-
A.
60%
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B.
70%
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C.
80%
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D.
90%
Solution
Efficiency = (Output Work / Input Energy) * 100 = (1200 J / 2000 J) * 100 = 60%.
Correct Answer: A — 60%
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Q. A person lifts a 10 kg box to a height of 2 m. What is the work done against gravity? (g = 9.8 m/s²)
-
A.
196 J
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B.
98 J
-
C.
20 J
-
D.
10 J
Solution
Work = mgh = 10 kg * 9.8 m/s² * 2 m = 196 J.
Correct Answer: A — 196 J
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Q. How much work is done when a force of 10 N moves an object 5 m in the direction of the force?
-
A.
25 J
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B.
50 J
-
C.
75 J
-
D.
100 J
Solution
Work = Force * Distance = 10 N * 5 m = 50 J.
Correct Answer: B — 50 J
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Q. How much work is done when a force of 30 N moves an object 4 m in the direction of the force?
-
A.
120 J
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B.
90 J
-
C.
60 J
-
D.
30 J
Solution
Work = Force * Distance = 30 N * 4 m = 120 J.
Correct Answer: A — 120 J
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Q. If a 10 kg object is raised to a height of 5 m, what is the work done against gravity? (g = 9.8 m/s²)
-
A.
490 J
-
B.
980 J
-
C.
150 J
-
D.
250 J
Solution
Work = m * g * h = 10 kg * 9.8 m/s² * 5 m = 490 J.
Correct Answer: B — 980 J
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Q. If a 10 N force is applied at an angle of 60 degrees to the horizontal while moving an object 3 m, what is the work done? (2020)
-
A.
15 J
-
B.
30 J
-
C.
25 J
-
D.
5 J
Solution
Work done = Force × Distance × cos(θ) = 10 N × 3 m × cos(60°) = 10 N × 3 m × 0.5 = 15 J
Correct Answer: A — 15 J
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Q. If a 1000 kg car is moving with a speed of 15 m/s, what is its kinetic energy?
-
A.
112,500 J
-
B.
225,000 J
-
C.
75,000 J
-
D.
150,000 J
Solution
Kinetic Energy = 0.5 × mass × velocity² = 0.5 × 1000 kg × (15 m/s)² = 112,500 J
Correct Answer: B — 225,000 J
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Q. If a 2 kg object is moving with a velocity of 15 m/s, what is its kinetic energy?
-
A.
225 J
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B.
150 J
-
C.
300 J
-
D.
450 J
Solution
Kinetic Energy = 1/2 * m * v^2 = 1/2 * 2 kg * (15 m/s)^2 = 225 J.
Correct Answer: A — 225 J
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Q. If a 2 kg object is moving with a velocity of 3 m/s, what is its kinetic energy?
-
A.
9 J
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B.
6 J
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C.
3 J
-
D.
12 J
Solution
Kinetic Energy = 0.5 * m * v² = 0.5 * 2 kg * (3 m/s)² = 9 J.
Correct Answer: A — 9 J
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Q. If a car accelerates from rest to a speed of 20 m/s, and its mass is 1000 kg, what is the kinetic energy of the car at that speed? (2020)
-
A.
200 J
-
B.
1000 J
-
C.
2000 J
-
D.
4000 J
Solution
Kinetic Energy = 0.5 × mass × velocity² = 0.5 × 1000 kg × (20 m/s)² = 200000 J = 2000 J
Correct Answer: C — 2000 J
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Q. If a car accelerates from rest to a speed of 20 m/s, what is the kinetic energy of the car if its mass is 1000 kg?
-
A.
200,000 J
-
B.
100,000 J
-
C.
50,000 J
-
D.
400,000 J
Solution
Kinetic Energy = 0.5 × mass × velocity² = 0.5 × 1000 kg × (20 m/s)² = 200,000 J
Correct Answer: B — 100,000 J
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Q. If a car with a mass of 1200 kg is moving at a speed of 15 m/s, what is its kinetic energy? (2021)
-
A.
13500 J
-
B.
9000 J
-
C.
18000 J
-
D.
27000 J
Solution
Kinetic Energy = 0.5 × mass × velocity² = 0.5 × 1200 kg × (15 m/s)² = 13500 J
Correct Answer: A — 13500 J
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Q. If a force of 20 N moves an object 5 m in the direction of the force, what is the work done?
-
A.
100 J
-
B.
50 J
-
C.
20 J
-
D.
200 J
Solution
Work = Force * Distance = 20 N * 5 m = 100 J.
Correct Answer: A — 100 J
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Q. If a person does 300 J of work in 15 seconds, what is their power output?
-
A.
20 W
-
B.
15 W
-
C.
25 W
-
D.
30 W
Solution
Power = Work / Time = 300 J / 15 s = 20 W
Correct Answer: A — 20 W
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Q. If a person lifts a 20 kg box to a height of 2 m, what is the work done against gravity? (g = 9.8 m/s²)
-
A.
392 J
-
B.
196 J
-
C.
588 J
-
D.
784 J
Solution
Work = m * g * h = 20 kg * 9.8 m/s² * 2 m = 392 J.
Correct Answer: B — 196 J
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