Physics

Problem

2.0\,\text{kg}

ball is projected vertically upward with a speed of

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

from ground level. At what height from the ground will its speed be

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

? (Take

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

) a)

9.2\,\text{m}

3.7\,\text{m}

5.5\,\text{m}

11\,\text{m}

Intuitive explanation

This problem is about energy conservation in vertical motion—the key insight is that mechanical energy (kinetic plus gravitational potential) stays constant as the ball rises and slows down. Rather than tracking the ball's position through time, you can directly relate the ball's speed at two different heights using the fact that the total energy at launch equals the total energy at any height. Set up the energy equation and solve for the unknown height.

Intuitive explanation

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