Question

An object of mass 2 kg is thrown up at a velocity of 10 ms^-1. Find the kinetic energy of the object at the time of the throw. Also, find the potential energy of the object at the highest point. Take the value of g as 10 ms^-2.

Answer 1

1. Given the mass of the object= 2 kg
Initial Velocity (v) of the object at the time of throw= 10 ms^-1
2. The energy possessed by an object by virtue of its motion is called kinetic energy.
The kinetic energy of an object of mass m and velocity v can be given as-
$K.E=\frac{m{v}^2}{2}$--------(I)
Substituting the value of m and v in equation (I) we get-
$$\begin{gathered} K.E=\frac{1}{2}\left(2kg\right){\left(10m{s}^{-1}\right)}^2 \\ K.E=\frac{1}{2}\left(2kg\right)\left(100m{s}^{-1}\right) \\ K.E=100J \end{gathered}$$
Hence kinetic energy of the object at the time of throw will be 100J.
3. According to the law of conservation of energy, the energy can neither be created nor be destroyed but it can only be transformed from one form to another.
When we throw an object with velocity v the decrease in kinetic energy (energy due to motion) is equal to an increase in the potential energy (energy due to height) of the object.
Therefore maximum potential energy at a height h will be equal to kinetic energy at ground level.
Hence at maximum height potential energy of the object will be equal to 100J.