1.Easy
A 0.5 kg ball is dropped from rest from a height of 35 m. Ignore air resistance. Find its speed v just before it hits the ground.
m = 0.5 kgh = 35 mg = 9.81 m/s²
v = m/s
Work & energy worksheet with answers
2.Easy
A 4 kg ball is dropped from rest from a height of 38 m. Ignore air resistance. Find its kinetic energy Ek just before it hits the ground.
m = 4 kgh = 38 mg = 9.81 m/s²
Ek = J
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 0.5. Find the stopping distance d.
v = 80 km/hμ = 0.5g = 9.81 m/s²
d = m
4.Medium
A 1200 kg car drives up a 6° slope at a constant 54 km/h. Air resistance and rolling resistance together amount to 450 N. Find the power P the wheels must deliver, in kW.
m = 1200 kgθ = 6°Fr = 450 Nv = 54 km/hg = 9.81 m/s²
P = kW
5.Hard
A 4 kg block is released from rest at height 2 m on a smooth ramp. At the bottom it crosses a rough horizontal strip 5 m long (μ = 0.25) and then runs onto a spring (k = 500 N/m) on a smooth surface. Find the maximum compression x of the spring.
m = 4 kgh = 2 mL = 5 mμ = 0.25k = 500 N/mg = 9.81 m/s²
x = cm
6.Hard
A 15 kg block starts from rest at the bottom of a 30° slope and is pulled up the slope by a constant force of 225 N parallel to the slope. The coefficient of kinetic friction is 0.3. Find the speed v of the block after it has moved 7 m up the slope.
m = 15 kgF = 225 Nθ = 30°μ = 0.3d = 7 mg = 9.81 m/s²
v = m/s
Answer key
- 1. v = 26.2 m/s
- 2. Ek = 1491 J
- 3. d = 50.34 m
- 4. P = 25.21 kW
- 5. x = 34.31 cm
- 6. v = 10.28 m/s
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