1.Easy
A 2 kg ball is dropped from rest from a height of 29 m. Ignore air resistance. Find its speed v just before it hits the ground.
m = 2 kgh = 29 mg = 9.81 m/s²
v = m/s
Work & energy worksheet with answers
2.Easy
A hoist lifts a 500 kg load at constant speed through a height of 5 m in 45 s. Find the average power P it delivers to the load, in W.
m = 500 kgh = 5 mt = 45 sg = 9.81 m/s²
P = W
3.Medium
A block slides from rest down a slope at 30° to the horizontal. The coefficient of kinetic friction is 0.3. Find its speed v after it has slid 14 m along the slope.
θ = 30°μ = 0.3d = 14 mg = 9.81 m/s²
v = m/s
4.Medium
A 1800 kg car drives up an 8° slope at a constant 90 km/h. Air resistance and rolling resistance together amount to 650 N. Find the power P the wheels must deliver, in kW.
m = 1800 kgθ = 8°Fr = 650 Nv = 90 km/hg = 9.81 m/s²
P = kW
5.Hard
An 8 kg block starts from rest at the bottom of a 15° slope and is pulled up the slope by a constant force of 45 N parallel to the slope. The coefficient of kinetic friction is 0.2. Find the speed v of the block after it has moved 7 m up the slope.
m = 8 kgF = 45 Nθ = 15°μ = 0.2d = 7 mg = 9.81 m/s²
v = m/s
6.Hard
A spring of stiffness 1000 N/m at the bottom of a 35° slope is compressed by 15 cm against a 3 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 = 3 kgk = 1000 N/mx = 15 cmθ = 35°μ = 0.15g = 9.81 m/s²
d = m
Answer key
- 1. v = 23.85 m/s
- 2. P = 545 W
- 3. v = 8.123 m/s
- 4. P = 77.69 kW
- 5. v = 4.083 m/s
- 6. d = 0.5489 m
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