Question

a motor car of mass 1200 kg is moving along a straight line with uniform velocity of 90 kilometre per hour. its velocity is slowed down to 18 kilometre per hour in 4 seconds by an unbalanced external force. Calculate the acceleration and change in momentum. Also calculate the magnitude of the force required point​

Answer 1

Solution:

Given:

Mass (car) = 1200 kg

Uniform velocity = 90 km/hr

Now,

Initial velocity of the car:

$\implies$ 90 km/h

$\implies$ 90 × 5/18 m/s

$\implies$ 25 m/s 

Final velocity of the car:

$\implies$ 18 km/h

$\implies$ 18 × 5/18 m/s

$\implies$ 5 m/s 

So, initial velocity is 25 m/s and final velocity is 5 m/s.

We know that:

$\boxed{\sf{Acceleration = \frac{(Final\:vel. - Initial\:vel.)}{Time\:taken}}}$

$\implies$ (25 - 5)/4

$\implies$ 5 m/s²

Now,

$\boxed{\sf{Change\:in\:momentum = m\:(f.v. - i.v.)}}$

$\implies$ 1200 × (25 - 5)

$\implies$ 1200 × 20

$\implies$ 24000 kg m/s 

We know that:

$\boxed{\sf{Force = \frac{Change\:in\:momentum}{Time}}}$

So:

$\implies$ 24000/4

$\implies$ 6000 N  

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Answered by: Niki Swar, Goa❤️