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

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

Step-by-step 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=(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=(1)/(2)m_gv^2` ...(1)

As
`m_b=20m_g`

Kinetic energy of a boy,

`K_b=(1)/(2)m_bv^2\\\\=(1)/(2)* 20m_g* v^2\ ....(2)`

From equation (1) and (2) :

`(K_g)/(K_b)=((1)/(2)m_gv^2)/((1)/(2)m_bv^2)\\\\=((1)/(2)m_gv^2)/((1)/(2)* 20 m_gv^2)\\\\(K_g)/(K_b)=(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.