Question

question from class 9 physics chapter forces and law of motion​​

Answer 1

Answer:

A sedan car of mass 200kg is moving with a certain velocity.

It is brought to rest by the application of brakes, within a distance of 20 m .

The force applied on it is 500 N

To find -

Average velocity of the car.

Solution -

We know that from Newtonian Motion -

F=ma

Here -

F = 500 N

M = 200 kg

a = ?

=> 500 = 200 a

=> a = (5 / 2 ) = 2.5 metres per second².

Now, this it's retardation.

According to the third law of motion -

V² = U² + 2as

V = Final Velocity = 0

U = Initial Velocity

A = acceleration = 2.5

S = displacement = 20 m

Substituting these values -

0 = U² - 2 × 2.5 × 20

=> U² = 100 m/s

=> U = 10 m/s or -10 m/s

This is the required answer.

Note that U can be positive as well as negative here, as this is velocity.