Question

A 10kg ball is thrown upward with a speed of 5 m/s
A. Find its potential energy when it reaches the highest point.
B. Calculate the maximum height it reaches.

Answer 1

Hint: Here we will use the relation between kinetic energy, mass and the velocity of an object. We also know that at maximum height only potential energy exists. Further, applying the given values in the relation gives us the required result.

Formula used: $K.E = \dfrac{1}{2}m{v^2}$
$h = \dfrac{{{v^2} - {u^2}}}{{2g}}$

Complete step by step answer:
1. When a ball of 10kg mass is thrown upward with a speed v of 5m/s, the kinetic energy of this ball can be written as:
$\eqalign{
  & K.E = \dfrac{1}{2}m{u^2} \cr
  & K.E = \dfrac{1}{2} \times 10 \times 5 \times 5 \cr
  & \Rightarrow K.E = 125J \cr
  & \therefore P.E = 125J \cr} $
As, we know at the maximum height the kinetic energy becomes potential energy:
2. To find the maximum height that the 10 kg ball reaches is given by:
$\eqalign{
 & h = \dfrac{{{v^2} - {u^2}}}{{2g}} = \dfrac{{{0^2} - {5^2}}}{{2 \times ( - 10)}} \cr
  & \therefore h = \dfrac{{25}}{{10}} = \dfrac{5}{2} \cr} $
Therefore, from the above two results we get the potential energy and the maximum height of the ball.

Additional Information:
As we know that the energy is defined as the ability to do work. Energy can be found in many things and can take different forms, like-kinetic energy is the energy of motion, and potential energy is energy due to an object's position or structure. Total energy of a system is given by the sum of kinetic energy and potential energy.
We also know that, according to the law of conservation of energy, energy can neither be created nor be destroyed; rather it can only be transferred from one form to another. Here, in this question electrical energy is transferred to heat energy.
We should also know about the power. It is the amount of energy transferred or converted per unit time. In the International System or S.I Unit of power is the watt. The S.I unit of power can also be written as one joule per second. Power is a scalar quantity, which means it has only magnitude not direction.

Note: We should remember that when an object's gains maximum height, then only potential energy exists, whereas kinetic energy exists when the object gains motion. We should remember that the laws of conservation of energy can never be violated in any case. According to the law of conservation of energy, energy can neither be created nor be destroyed; rather it can only be transferred from one form to another.