Read the following everyday situations and answer the questions that follow
PHYSICS · Multi-part · CBSE · Physics · Work and Energy · Work and Energy
Problem
Read the following everyday situations and answer the questions that follow. No numerical calculations are required; give qualitative explanations based on energy considerations.
(i) A cyclist of mass 60kg stops pedalling and rolls down a frictionless hill, gaining speed as she descends. Explain how her kinetic and potential energies change and state what happens to her total mechanical energy.
(ii) A stone is thrown vertically upward with an initial speed of 14m s−1. Describe qualitatively the variation of its kinetic energy and potential energy from the instant of projection until it reaches its highest point. Comment on the total mechanical energy during this interval.
(iii) Two skaters start simultaneously from rest at the same height h on two different frictionless ramps—one straight and one curved. They both reach the bottom. Explain whether their speeds and their mechanical energies at the bottom will be the same or different, giving reasons.