1.Easy
A 10 kg ball is dropped from rest from a height of 12 m. Ignore air resistance. Find its speed v just before it hits the ground.
m = 10 kgh = 12 mg = 9.81 m/s²
v = m/s
Work & energy worksheet with answers
2.Easy
A crate is pulled 13 m along a level floor by a rope that makes 50° with the horizontal. The tension in the rope is 170 N. Find the work W done by the rope on the crate.
F = 170 Nd = 13 mθ = 50°
W = J
3.Medium
A car travelling at 80 km/h on a level road brakes hard and skids to a stop with its wheels locked. The coefficient of kinetic friction between the tyres and the road is 0.7. Find the stopping distance d.
v = 80 km/hμ = 0.7g = 9.81 m/s²
d = m
4.Medium
A car travelling at 120 km/h on a level road brakes hard and skids to a stop with its wheels locked. The coefficient of kinetic friction between the tyres and the road is 0.8. Find the stopping distance d.
v = 120 km/hμ = 0.8g = 9.81 m/s²
d = m
5.Hard
A 10 kg block rests on a rough horizontal table (μ = 0.3). A light string runs from it over a smooth pulley at the edge of the table to a hanging 5 kg block. The system is released from rest. Find the speed v of the blocks after the hanging block has dropped 3 m.
m1 = 10 kgm2 = 5 kgμ = 0.3d = 3 mg = 9.81 m/s²
v = m/s
6.Hard
A spring of stiffness 800 N/m at the bottom of a 20° slope is compressed by 15 cm against a 0.5 kg block and released. The coefficient of kinetic friction between block and slope is 0.25. How far d up the slope does the block travel from the release point before it stops? (Ignore the short distance over which the spring pushes, i.e. take friction and gravity over the whole distance d.)
m = 0.5 kgk = 800 N/mx = 15 cmθ = 20°μ = 0.25g = 9.81 m/s²
d = m
Answer key
- 1. v = 15.34 m/s
- 2. W = 1421 J
- 3. d = 35.96 m
- 4. d = 70.79 m
- 5. v = 2.801 m/s
- 6. d = 3.18 m
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