Question

A motorcar is moving with a velocity of 108km/hr and it takes 4sec to stop after the the breaks are applied.find the force excerted by the breaks on motorcar if its mass along with the passengers is 500 Kg

Answer 1

Given:

Velocity of motor car= 108 km/hr

Time taken to stop= 4 sec

Mass of Motor car along with passengers =500kg

To Find:

Force exerted by the breaks on motorcar

Solution:

We know that,

• For a body in motion

$\pink{\boxed{\bf{Acceleration=\frac{Change\:in\:Velocity}{Time}}}}$

• Expression of force is given by

$\red{\boxed{\bf{F=ma}}}$

where,

F is force applied

m is mass of body

a is acceleration of the body

Now,

For the given motor car,

Velocity of Motor car= 108 km/hr

On converting velocity in m/s, we get

$\sf{Velocity\:of\:Motorcar=108 km/hr=108\times\dfrac{5}{18}=30\:m/s}$

Also,

$\longrightarrow\mathrm{Acceleration=\dfrac{Change\:in\:Velocity}{Time}}$

$\longrightarrow\mathrm{Acceleration=\dfrac{0-30}{4}=\dfrac{-15}{2}m/s^{2}}$

So,

$\longrightarrow\mathrm{F=ma}$

$\longrightarrow\mathrm{F=500\times\dfrac{-15}{2}}$

$\longrightarrow\mathrm{F=250\times(-15)}$

$\longrightarrow\mathrm{F=-3750\:N}$

Therefore, the force exerted by the breaks on motorcar is -3750 N.