Work & energy worksheet with answers

Free printable Work & energy worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
400 kgh = 24 mt = 10 s

A hoist lifts a 400 kg load at constant speed through a height of 24 m in 10 s. Find the average power P it delivers to the load, in kW.

m = 400 kgh = 24 mt = 10 sg = 9.81 m/s²
P = kW
2.Easy
F = 180 N15°d = 12 m

A crate is pulled 12 m along a level floor by a rope that makes 15° with the horizontal. The tension in the rope is 180 N. Find the work W done by the rope on the crate.

F = 180 Nd = 12 mθ = 15°
W = J
3.Medium
20°d = 3 mμ = 0.25

A block slides from rest down a slope at 20° to the horizontal. The coefficient of kinetic friction is 0.25. Find its speed v after it has slid 3 m along the slope.

θ = 20°μ = 0.25d = 3 mg = 9.81 m/s²
v = m/s
4.Medium
0.2 kgk = 1000 N/mh = ?

A toy launcher has a vertical spring of stiffness 1000 N/m. A 0.2 kg ball is placed on it and the spring is compressed by 4 cm, then released. Ignoring air resistance and the spring’s mass, find the height h the ball rises, measured from its position when the spring was compressed.

m = 0.2 kgk = 1000 N/mx = 4 cmg = 9.81 m/s²
h = m
5.Hard
F = 85 N30°μ = 0.38 kg

An 8 kg block starts from rest at the bottom of a 30° slope and is pulled up the slope by a constant force of 85 N parallel to the slope. The coefficient of kinetic friction is 0.3. Find the speed v of the block after it has moved 5 m up the slope.

m = 8 kgF = 85 Nθ = 30°μ = 0.3d = 5 mg = 9.81 m/s²
v = m/s
6.Hard
k = 3000 N/m15°μ = 0.251 kg

A spring of stiffness 3000 N/m at the bottom of a 15° slope is compressed by 5 cm against a 1 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 = 1 kgk = 3000 N/mx = 5 cmθ = 15°μ = 0.25g = 9.81 m/s²
d = m

Answer key

  1. 1. P = 9.418 kW
  2. 2. W = 2086 J
  3. 3. v = 2.511 m/s
  4. 4. h = 0.4077 m
  5. 5. v = 5.631 m/s
  6. 6. d = 0.7641 m

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