Three identical stones A, B and C are at different heights above the ground and…

PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

Three identical stones A, B and C are at different heights above the ground and moving vertically as described below. • Stone A is at a height of

5\,\text{m}

and momentarily at rest. • Stone B is at a height of

3\,\text{m}

and moving downward with a speed of

6\,\text{m s}^{-1}

. • Stone C is at a height of

1\,\text{m}

and moving downward with a speed of

8\,\text{m s}^{-1}

. Assume

g = 9.8\,\text{m s}^{-2}

and neglect air resistance. Answer the following questions without doing any numerical calculation of energy values. (i) Arrange the stones in descending order of their kinetic energy. (ii) Arrange the stones in descending order of their gravitational potential energy. (iii) Arrange the stones in descending order of their total mechanical energy. (iv) Give clear reasoning for each of the three orderings you have written above.

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