1.Easy
A crate is pulled 12 m along a level floor by a rope that makes 50° with the horizontal. The tension in the rope is 100 N. Find the work W done by the rope on the crate.
F = 100 Nd = 12 mθ = 50°
W = J
Work & energy worksheet with answers
2.Easy
A 10 kg ball is dropped from rest from a height of 3 m. Ignore air resistance. Find its kinetic energy Ek just before it hits the ground.
m = 10 kgh = 3 mg = 9.81 m/s²
Ek = J
3.Medium
A 2.5 kg block slides 3 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 = 2.5 kgθ = 40°μ = 0.15d = 3 mg = 9.81 m/s²
Wf = J
4.Medium
A 1 kg ball hangs on a light string of length 3 m. It is pulled aside until the string makes 20° with the vertical and released from rest. Find the tension T in the string when the ball passes the lowest point.
m = 1 kgL = 3 mθ = 20°g = 9.81 m/s²
T = N
5.Hard
A spring of stiffness 3000 N/m at the bottom of a 35° slope is compressed by 10 cm against a 3 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 = 3 kgk = 3000 N/mx = 10 cmθ = 35°μ = 0.25g = 9.81 m/s²
d = m
6.Hard
A 10 kg block starts from rest at the bottom of a 25° slope and is pulled up the slope by a constant force of 95 N parallel to the slope. The coefficient of kinetic friction is 0.2. Find the speed v of the block after it has moved 5 m up the slope.
m = 10 kgF = 95 Nθ = 25°μ = 0.2d = 5 mg = 9.81 m/s²
v = m/s
Answer key
- 1. W = 771.3 J
- 2. Ek = 294.3 J
- 3. Wf = 8.454 J
- 4. T = 10.99 N
- 5. d = 0.6548 m
- 6. v = 5.98 m/s
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