Question

A 4.00 kg stone is dropped from a height of 145 m. What is the stone's potential and kinetic energy respectively when it is 50.0 m from the ground?

Answer 1

Answer;

D - 1,960 J, 3,720 J

Explanation;

• The stone is initially at a height of 100 m from where it is dropped. The gravitational potential energy of an object with mass m at a height h from the ground is PE = mgh where g is the acceleration due to gravity.
• At a height of 145 m from the ground, the potential energy of the 3 kg stone is 4×9.8×145 = 5,684 J, approximately; 5680 Joules.

At a height of 50 m from the ground, the potential energy will be;

= 4 × 9.8 × 50

= 1960 Joules

This means that some of the energy possessed by the stone at a height of 145 m was converted to kinetic energy.

Therefore; the energy that was converted to kinetic energy will be;

= 5,680 J - 1960 J

= 3,724 Joules

Approximately kinetic energy is 3,720 Joules

Therefore;

The Potential energy is 1960 Joules and Kinetic energy is 3,720 Joules