Q1. A block of mass 2 kg is lifted to a height of 5 m. What is the work done against gravity? (g = 9.8 m/s²)
Solution:
Work done = mgh = 2 kg * 9.8 m/s² * 5 m = 98 J.
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Q2. A force of 10 N is applied to move an object 5 m in the direction of the force. What is the work done by the force?
Solution:
Work done (W) = Force (F) × Distance (d) × cos(θ). Here, θ = 0° (force and displacement are in the same direction). W = 10 N × 5 m × cos(0°) = 10 N × 5 m = 50 J.
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Q3. If a 2 kg object is lifted to a height of 3 m, what is the potential energy gained by the object? (g = 9.8 m/s²)
Solution:
Potential Energy (PE) = mgh = 2 kg × 9.8 m/s² × 3 m = 58.8 J.
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Q4. An object is lifted vertically 10 m. If the mass of the object is 5 kg, what is the gravitational potential energy gained?
Solution:
Potential Energy (PE) = mgh = 5 kg * 9.8 m/s² * 10 m = 490 J.
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Q5. A cyclist is moving at a speed of 15 m/s. If the mass of the cyclist and the bicycle is 75 kg, what is the total kinetic energy?
Solution:
KE = 0.5 × m × v² = 0.5 × 75 kg × (15 m/s)² = 0.5 × 75 × 225 = 8437.5 J.
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Q6. A cyclist does 600 J of work to climb a hill. If he takes 30 seconds, what is his average power output? (2022)
Solution:
Power = Work / Time = 600 J / 30 s = 20 W.
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Q7. If a 1000 kg car is moving at 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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Q8. 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.
⏱ Time: 0s
Q9. A machine does 1200 J of work in 60 seconds. What is its efficiency if the input energy is 2000 J? (2022)
