Question

A boy and girl are running with the same speed.if the mass of the boy is 20 times that of girl find the kinectic energy

Answer 1

Answer:

The kinetic energy of the boy is 20 times that of the kinetic energy of the girl.

Explanation:

It is given that,

The mass of the boy is 20 times that of girl.

Let $m_b$ and $m_g$ are the mases of boy and the girls.

A boy and girl are running with the same speed.

The formula for the kinetic energy is given by :

$E=\dfrac{1}{2}mv^2$

Where m is mass and v is speed

As speed is same for both boy and girl.

Kinetic energy of a girl,

$K_g=\dfrac{1}{2}m_gv^2$ ...(1)

As $m_b=20m_g$

Kinetic energy of a boy,

$K_b=\dfrac{1}{2}m_bv^2\\\\=\dfrac{1}{2}\times 20m_g\times v^2\ ....(2)$

From equation (1) and (2) :

$\dfrac{K_g}{K_b}=\dfrac{\dfrac{1}{2}m_gv^2}{\dfrac{1}{2}m_bv^2}\\\\=\dfrac{\dfrac{1}{2}m_gv^2}{\dfrac{1}{2}\times 20 m_gv^2}\\\\\dfrac{K_g}{K_b}=\dfrac{1}{20}\\\\K_b=20K_g$

So, the kinetic energy of the boy is 20 times that of the kinetic energy of the girl. Hence, this is the required solution.