Question

A person of mass 50 kg standing on a smooth horizontal plane of ice throws a body of mass 5 kg with velocity 10 m/s. Then the total kinetic energy of person and body is
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Answer 1

Given:

A person of mass 50 kg standing on a smooth horizontal plane of ice throws a body of mass 5 kg with velocity 10 m/s.

To find:

Total energy if person and body?

Calculation:

• First of all, we will calculate the velocity with which the person moves after throwing the body. This can be done with CONSERVATION OF LINEAR MOMENTUM principle.

$\rm \: 0 + 0 = 50v + (5 \times 10)$

$\rm \implies\: 50v = - 50$

$\rm \implies\: v = - 1 \: m {s}^{ - 1}$

Now, total kinetic energy will be :

$\rm KE_{total} = KE_{man} + KE_{body}$

$\rm \implies KE_{total} = \{ \dfrac{1}{2} \times 50 \times {( - 1)}^{2} \} + \{ \dfrac{1}{2} \times 5 \times {(10)}^{2} \}$

$\rm \implies KE_{total} = 25 + 250$

$\rm \implies KE_{total} =275 \: joule$

So, total KE is 275 Joule