A bicyclist initially travels at a steady 8 m/s for 100 seconds on a straight le

Question

A bicyclist initially travels at a steady 8 m/s for 100 seconds on a straight level road, and then takes 40 seconds to slow to 5 m/s. Three English majors discussing this situation make the following contentions about the bicycle's kinetic energy. With which, if any, do you agree? Explain why.


A.Axel: "The bicycle is just going to slow down naturally. It doesn't take any work for something to slow down."
B.Bram: "I disagree. The speed of the bike decreased, so there is a change in kinetic energy. That means work was done on the bike."
C.Cassie: "I think Axel is right that no work was done, but I don't agree with his reason. There is no work being done here because there are no external forces being exerted."
D.None of them are correct.

Explanation / Answer

B.Bram: "I disagree. The speed of the bike decreased, so there is a change in kinetic energy. That means work was done on the bike."

we know that work done by all forces = change in kinetic energy

since there is change in speed kinetic energy is changed therefore work is done on the cycle

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