Amy and Josh are coasting on their bicycles down a 10 degree slop at 15 m/s thro

Question

Amy and Josh are coasting on their bicycles down a 10 degree slop at 15 m/s through still air. The mass of Amy and her bicycle is 60 kg. The mass of Josh and his bicylce is 90 kg. The cross-sectional are of Amy and her bicycle is 0.45, while the cross-sectional area of Josh and his bicycle is 0.60. The drag coefficient for both cyclists is 0.70. Other than gravity and air resistance, the external forces acting on the two bicycle and rider systems are the same. Which cyclist is more affected by air resistance?

The answer is Amy. How would you answer this using the equation for drag?

Explanation / Answer

in drags equation the velocities of both bodies are the same and medium in which they travel is air.It is stated in the question as only gravity and air resistance differ on both of them other exter nal forces are the same,so if me consider the drags force it depends only on their surface area so larger the surface area larger the drag force i.e. josh will be having larger drag force than amy (0.45D<0.60D).But if we consider the -ve accelaration caused bye this force it is more for amy than josh as mass of josh is more compared to amy.So amy experiences more air resistance than josh.

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