Question

A boy weighing 40 kg makes a high jump of 1.5 m. What is his kinetic and potential at the highest point?

Answer 1

Hint: The potential energy is the energy that a body has due to its position from a certain point and kinetic energy depends on the value of velocity. The velocity at the highest point is zero.

Complete step by step answer:A boy of mass (m) = 40 kg makes a high jump of height (h) = 1.5 m. Initially when the boy is standing on the ground and makes a jump, his kinetic energy is K and potential energy is zero.
The kinetic energy is defined as the energy possessed by a body by virtue of its state of motion and the potential energy is the energy possessed by a body by virtue of its specific position or changed configuration. So, when the boy just makes a jump, he possesses some kinetic energy as he jumps with some velocity and potential energy is zero as its height from the ground is zero.
When the boy reaches the highest point, kinetic energy (K) of the boy completely changes to potential energy and the body momentarily comes to rest. At this position, the boy is still under the effect of the force of gravity. The initial kinetic energy provided to the boy at the ground to reach the highest point is equal to the potential energy (P) of the boy at that position.
Let the height of the boy at this position be h.
$P = mgh$ where g is acceleration due to gravity.
$P = 40 \times 10 \times 1.5$
$P = 600J$
The kinetic energy at the highest point becomes zero as whole initial energy changes to potential energy.

Note:The potential energy at the highest point means the energy possessed by the body due to its height from the ground and kinetic energy is zero as velocity becomes zero.