A child rides a skateboard through a shallow concrete bowl. Fig. 1 shows two positions. At point A the child is momentarily stationary at the top edge. At p...
Question 1 Report
A child rides a skateboard through a shallow concrete bowl. Fig. 1 shows two positions. At point A the child is momentarily stationary at the top edge. At point B the child is near the lowest point and has high velocity. Air resistance and friction between the wheels and concrete are small but not zero. The child does not use their feet to push during this journey.
(a) What happens to the child’s gravitational potential energy store between A and B? [1]
(b) Give the energy store that is largest at point B. [1]
(c) Explain why the child will not return to exactly the same height as point A. [3]
Answer Details
As the skateboarder moves downhill, energy changes between stores, but friction means not all of it remains available for the return climb.
- (a) The gravitational potential energy store decreases. [1]
- (b) At the low point, the largest store is the kinetic energy store. [1]
- (c) Friction at the wheels and air resistance act during the journey. They transfer energy to thermal energy stores of the wheels, concrete and air. Therefore less mechanical energy remains to increase gravitational potential energy, so the child cannot return to the original height. [3]
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