1.Easy
A 5 kg ball is dropped from rest from a height of 49 m. Ignore air resistance. Find its kinetic energy Ek just before it hits the ground.
m = 5 kgh = 49 mg = 9.81 m/s²
Ek = J
Work & energy worksheet with answers
2.Easy
A 2 kg block slides at 2 m/s on a smooth horizontal surface into a spring of stiffness 2000 N/m. Find the maximum compression x of the spring, in cm.
m = 2 kgv = 2 m/sk = 2000 N/m
x = cm
3.Medium
A 1200 kg car drives up a 4° slope at a constant 54 km/h. Air resistance and rolling resistance together amount to 500 N. Find the power P the wheels must deliver, in kW.
m = 1200 kgθ = 4°Fr = 500 Nv = 54 km/hg = 9.81 m/s²
P = kW
4.Medium
A 10 kg block slides 3 m down a slope at 25° to the horizontal, with a coefficient of kinetic friction of 0.1. Find the work Wf done against friction.
m = 10 kgθ = 25°μ = 0.1d = 3 mg = 9.81 m/s²
Wf = J
5.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 85 N parallel to the slope. The coefficient of kinetic friction is 0.1. Find the speed v of the block after it has moved 8 m up the slope.
m = 10 kgF = 85 Nθ = 25°μ = 0.1d = 8 mg = 9.81 m/s²
v = m/s
6.Hard
A spring of stiffness 2000 N/m at the bottom of a 20° slope is compressed by 12 cm against a 2 kg block and released. The coefficient of kinetic friction between block and slope is 0.15. 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 = 2 kgk = 2000 N/mx = 12 cmθ = 20°μ = 0.15g = 9.81 m/s²
d = m
Answer key
- 1. Ek = 2403 J
- 2. x = 6.325 cm
- 3. P = 19.82 kW
- 4. Wf = 26.67 J
- 5. v = 7.446 m/s
- 6. d = 1.52 m
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