Question

A student drops a tennis ball from the top of a building as shown in the picture air resistance is negligible. Explain how the student can determine the height of the building if the kinetic Energy of the tennis ball is known when it hits the ground. And your explanation use the terms kinetic energy, gravitational potential energy, acceleration due to gravity mass and height

Answer 1

We can use potential energy to solve. Remember, your height and your gravity need to have the same sign, as they are moving in the same direction (downward). Either make them both negative, or use an absolute value.

Using conservation of energy, we know that PEtop=KEbottom. This tells us that the potential energy at the top of the hill is all converted to kinetic energy at the bottom of the hill. We can substitute the equations for potential energy and kinetic energy.

mgh=12mv2

The masses cancel out.

gh=12v2

Plug in the values, and solve for the velocity.