1.Easy
A 5 kg ball is dropped from rest from a height of 42 m. Ignore air resistance. Find its kinetic energy Ek just before it hits the ground.
m = 5 kgh = 42 mg = 9.81 m/s²
Ek = J
Work & energy worksheet with answers
2.Easy
A 1 kg ball is dropped from rest from a height of 20 m. Ignore air resistance. Find its speed v just before it hits the ground.
m = 1 kgh = 20 mg = 9.81 m/s²
v = m/s
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 0.4. Find the stopping distance d.
v = 80 km/hμ = 0.4g = 9.81 m/s²
d = m
4.Medium
A toy launcher has a vertical spring of stiffness 2000 N/m. A 0.5 kg ball is placed on it and the spring is compressed by 5 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 = 0.5 kgk = 2000 N/mx = 5 cmg = 9.81 m/s²
h = m
5.Hard
A spring of stiffness 2000 N/m at the bottom of a 40° slope is compressed by 5 cm against a 0.5 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 = 0.5 kgk = 2000 N/mx = 5 cmθ = 40°μ = 0.15g = 9.81 m/s²
d = m
6.Hard
A 10 kg block is released from rest at height 2 m on a smooth ramp. At the bottom it crosses a rough horizontal strip 4 m long (μ = 0.2) and then runs onto a spring (k = 500 N/m) on a smooth surface. Find the speed v of the block when it reaches the spring.
m = 10 kgh = 2 mL = 4 mμ = 0.2k = 500 N/mg = 9.81 m/s²
v = m/s
Answer key
- 1. Ek = 2060 J
- 2. v = 19.81 m/s
- 3. d = 62.92 m
- 4. h = 0.5097 m
- 5. d = 0.6727 m
- 6. v = 4.852 m/s
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