A 29.0 kg child slides down a long slide in a playground. She starts from rest a

Question

A 29.0 kg child slides down a long slide in a playground. She starts from rest at a height h1 of 21.00 m. When she is partway down the slide, at a height h2 of 9.00 m, she is moving at a speed of 7.00 m/s.

Calculate the mechanical energy lost due to friction (as heat, etc.).

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A skier (m=63.0 kg) starts sliding down from the top of a ski jump with negligible friction and takes off horizontally.

If h = 5.00 m and D = 12.1 m, find H.

Find her total kinetic energy as she reaches the ground.

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A car of mass 820.0 kg accelerates away from an intersection on a horizontal road. When the car speed is 37.4 km/hr (10.4 m/s), the net power which the engine supplies is 4500.0 W (in addition to the extra power required to make up for air resistance and friction). Calculate the acceleration of the car at that time.

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It takes a minimum distance of 66.64 m to stop a car moving at 14.0 m/s by applying the brakes (without locking the wheels). Assume that the same frictional forces apply and find the minimum stopping distance when the car is moving at 30.0 m/s.

Explanation / Answer

1) loss of mechanical energy = initail mechanical energy - final mechaincal energy

= 29*9.8*21 - (29*9.8*9 + 0.5*29*7^2)

= 2700 J

2) need figure to solve the problem

3) Apply, P = F*v

==> F = P/v

= 4500/10.4

= 432.7 N

so, a = F/m

= 432.7/820

= 0.528 m/s^2

4) minimum stopping distance = 66.64*(30/14)^2

= 306 m

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