Question

A car is moving with a uniform velocity of 30 m s
It is stopped in 2 s by applying a force of 1500 N
through its brakes. Calculate : (a) the change in
momentum of car, (b) the retardation produced in
car, and (c) the mass of the car.
Ans. (a) 3000 kg m s-1 (b) 15 m s-2 (c) 100 kg​

Answer 1

Answer:

first we will find the acceleration

v-u/t

v is equal to 0

u is equal to 30 metre per second

t is equal to 2 second

0-30/2

-15m/s²

F=ma

1500N=m×-15

1500N/15= m

100 kg = mass

change in momentum

mv-mu/t

100×0 - 100×30/2

3000/2

-1500kgm/s

Answer 2

Given:-

• Initial velocity , u = 30m/s

• Final velocity , v = 0m/s

• Time taken , t = 2s

• Force , F = 1500N

To Find:-

(a) change in Momentum

(b) Retardation

(c) Mass of the car

Solution:-

(b)

Firstly we calculate the retardation of the car

By using 1st equation of motion

• v = u+at

Substitute the value we get

→ 0 = 30×a×2

→ -30 = a×2

→ a = -30/2

→ a = -15m/s²

∴ The retardation of the car is 15m/s²

_______________________________________

(c)

As we know that Force is the product of mass and acceleration

• F = m×a

Substitute the value we get

→ 1500 = m ×15

→ m = 1500/15

→ m = 100kg

∴ The Mass of the car is 100kg.

_______________________________________

(a)

Change in Momentum

• ∆p = mᵥ - mᵢ

∆p = m (v-u)

Substitute the value we get

→ ∆p = 100 (0-30)

→ ∆p = 100×(-30)

→ ∆p = -3000kgm/s

∴The change in Momentum is 3000 kgm/s