1.Easy
A hoist lifts an 80 kg load at constant speed through a height of 26 m in 30 s. Find the average power P it delivers to the load, in W.
m = 80 kgh = 26 mt = 30 sg = 9.81 m/s²
P = W
Work & energy worksheet with answers
2.Easy
A hoist lifts a 400 kg load at constant speed through a height of 13 m in 20 s. Find the average power P it delivers to the load, in kW.
m = 400 kgh = 13 mt = 20 sg = 9.81 m/s²
P = kW
3.Medium
A 5 kg ball hangs on a light string of length 3 m. It is pulled aside until the string makes 70° with the vertical and released from rest. Find the tension T in the string when the ball passes the lowest point.
m = 5 kgL = 3 mθ = 70°g = 9.81 m/s²
T = N
4.Medium
A 5 kg block slides 7 m down a slope at 40° to the horizontal, with a coefficient of kinetic friction of 0.15. Find the work Wf done against friction.
m = 5 kgθ = 40°μ = 0.15d = 7 mg = 9.81 m/s²
Wf = J
5.Hard
A 15 kg block starts from rest at the bottom of a 15° slope and is pulled up the slope by a constant force of 135 N parallel to the slope. The coefficient of kinetic friction is 0.2. Find the speed v of the block after it has moved 3 m up the slope.
m = 15 kgF = 135 Nθ = 15°μ = 0.2d = 3 mg = 9.81 m/s²
v = m/s
6.Hard
A 10 kg cart is released from rest at a height of 8.8 m on a smooth track that leads into a vertical circular loop of radius 2.5 m. Find the normal force N the track exerts on the cart at the top of the loop.
m = 10 kgh = 8.8 mR = 2.5 mg = 9.81 m/s²
N = N
Answer key
- 1. P = 680.2 W
- 2. P = 2.551 kW
- 3. T = 113.6 N
- 4. Wf = 39.45 J
- 5. v = 5.234 m/s
- 6. N = 200.1 N
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