Work, Energy & Power

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Q1. What is the power output of a motor that does 3000 J of work in 15 seconds?

Solution:

Power = Work / Time = 3000 J / 15 s = 200 W.

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Q2. What is the work done when a force of 15 N moves an object 3 m at an angle of 0 degrees to the direction of motion?

Solution:

Work = Force * Distance * cos(θ) = 15 N * 3 m * cos(0°) = 45 J.

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Q3. A car does 5000 J of work in moving a distance of 100 m. What is the average force exerted by the car? (2023)

Solution:

Average Force = Work done / Distance = 5000 J / 100 m = 50 N

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Q4. A car accelerates from rest to a speed of 20 m/s. If its mass is 1000 kg, what is the kinetic energy of the car at this speed? (2000)

Solution:

Kinetic Energy (KE) = 0.5 × m × v² = 0.5 × 1000 kg × (20 m/s)² = 0.5 × 1000 × 400 = 200000 J.

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Q5. If a 1000 kg car is moving with a speed of 15 m/s, what is its kinetic energy?

Solution:

Kinetic Energy = 0.5 × mass × velocity² = 0.5 × 1000 kg × (15 m/s)² = 112,500 J

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Q6. A car accelerates from rest to a speed of 20 m/s. If its mass is 1000 kg, what is the kinetic energy of the car at that speed?

Solution:

Kinetic Energy (KE) = 0.5 × m × v² = 0.5 × 1000 kg × (20 m/s)² = 0.5 × 1000 × 400 = 200,000 J.

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Q7. A 3 kg object is dropped from a height of 5 m. What is the potential energy at the top? (g = 9.8 m/s²)

Solution:

PE = mgh = 3 kg × 9.8 m/s² × 5 m = 147 J.

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Q8. A 50 kg object is moving with a velocity of 4 m/s. What is its kinetic energy?

Solution:

Kinetic Energy (KE) = 0.5 * m * v² = 0.5 * 50 kg * (4 m/s)² = 400 J.

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Q9. If a 2 kg object is moving with a velocity of 15 m/s, what is its kinetic energy?

Solution:

Kinetic Energy = 1/2 * m * v^2 = 1/2 * 2 kg * (15 m/s)^2 = 225 J.

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Q10. A force of 10 N is applied to move a box 5 m across a floor. What is the work done by the force?

Solution:

Work done = Force × Distance = 10 N × 5 m = 50 J