A 35 kg child slides down a playground slide at a constant speed . The slide has

Question

A 35 kg child slides down a playground slide at a constant speed. The slide has a height of 3.4 m and is 8.0 m long.

Part A

Using the law of conservation of energy, find the magnitude of the kinetic friction force acting on the child.

Express your answer to two significant figures and include the appropriate units.

A 35 kg child slides down a playground slide at a constant speed. The slide has a height of 3.4 m and is 8.0 m long.

Part A

Using the law of conservation of energy, find the magnitude of the kinetic friction force acting on the child.

Express your answer to two significant figures and include the appropriate units.

Explanation / Answer

The friction force F is parallel to the slope and is constant in magnitude, so its work is
W = - F d
with d = length of the slide.

This work equals the los in potential energy
U = m g h

Therefore:
- F d = m g h
F = - m g h / d = - 35 x 9.8 x (- 3.4) / 8.0 = 145.775 N

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