Kinetic Energy Solution

Assume a rider having a mass of 70 kg is perched at the top of the hill shown.
Suppose that 3,000 J of work is done against friction as the rider travels from the top position P1(at 50 m) to the second hump position P2(at 35 m).

Question: Will the rider make it to the top of the second hump (position P2) if no kinetic energy is given to the rider at the start of the motion?

  1. No
  2. Yes
  3. It depends on other factors
Solution:
Yes. The difference between the potential energy at position P1 and position P2 is:
(70 × 10 × 50 = 35,000 J) − (70 × 10 × 35 = 24,500 J) = 10,500 J,
plus loss to friction (3,000 J) is less than the KE available at the beiginning of the motion.



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Date of last modification: Summer , 2019