1.Easy
A 2 kg ball is dropped from rest from a height of 25 m. Ignore air resistance. Find its kinetic energy Ek just before it hits the ground.
m = 2 kgh = 25 mg = 9.81 m/s²
Ek = J
Work & energy worksheet with answers
2.Easy
A crate is pulled 6 m along a level floor by a rope that makes 20° with the horizontal. The tension in the rope is 90 N. Find the work W done by the rope on the crate.
F = 90 Nd = 6 mθ = 20°
W = J
3.Medium
A 1200 kg car drives up an 8° slope at a constant 72 km/h. Air resistance and rolling resistance together amount to 650 N. Find the power P the wheels must deliver, in kW.
m = 1200 kgθ = 8°Fr = 650 Nv = 72 km/hg = 9.81 m/s²
P = kW
4.Medium
A car travelling at 40 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 0.5. Find the stopping distance d.
v = 40 km/hμ = 0.5g = 9.81 m/s²
d = m
5.Hard
A 5 kg block is released from rest at height 3.5 m on a smooth ramp. At the bottom it crosses a rough horizontal strip 4.5 m long (μ = 0.25) and then runs onto a spring (k = 1000 N/m) on a smooth surface. Find the speed v of the block when it reaches the spring.
m = 5 kgh = 3.5 mL = 4.5 mμ = 0.25k = 1000 N/mg = 9.81 m/s²
v = m/s
6.Hard
A 2.5 kg block is released from rest at height 1.5 m on a smooth ramp. At the bottom it crosses a rough horizontal strip 5 m long (μ = 0.1) and then runs onto a spring (k = 500 N/m) on a smooth surface. Find the maximum compression x of the spring.
m = 2.5 kgh = 1.5 mL = 5 mμ = 0.1k = 500 N/mg = 9.81 m/s²
x = cm
Answer key
- 1. Ek = 490.5 J
- 2. W = 507.4 J
- 3. P = 45.77 kW
- 4. d = 12.58 m
- 5. v = 6.826 m/s
- 6. x = 31.32 cm
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