Question

a body of mass 5 kg is thrown vertically upwards with a speed of 10 m/s . what is its kinetic energy when it is thrown ?find its potential energy when it reaches at the higest point . also find the maximum height attained by the body ( g=10m/s2)

Answer 1

The kinetic energy of the mass at the point through which it is thrown is given by
$$\begin{gathered} \mathrm{KE}=\frac{1}{2}m{v}^2 \\ \mathrm{KE}=\frac{1}{2}\times 5\times {10}^2=250\mathrm{J} \end{gathered}$$
Taking the potential energy at the point of throwing to be zero.
Total energy = 250 + 0 = 250 J

At highest point

Kinetic energy = 0
Let the potential energy be P
Applying conservation of mechanical energy

250 + 0 = 0 + P
$\Rightarrow$P = 250 J
Let the maximum height attained by the body be h
Potential energy is given by mgh

where,
m = mass of the body
g = acceleration due to gravity
h = height

mgh = 250 J

5$\times$10$\times$h = 250
$\Rightarrow$h = 5 m