Question

A motorcar is moving with a velocity of 108 km/h and it takes 4 s to
stop after the brakes are applied
Calculate the force exerted by the
brakes on the motorcar if its mass along
with the passengers is 1000 kg.
​

Answer 1

Answer:

-7500 Newtons

Explanation:

Given:

• Initial velocity of motorcar = u = 108 km/h

108 km/h = $108 \times \frac{5}{18} = 30 \ m/s$

• Time taken = t = 4 seconds
• Mass of the motorcar along with the passengers = 1000 kg's
• Final velocity of the motorcar = v = 0 m/s

To find:

• Force exerted by brakes on the motorcar (f)

Force = $\frac{Mass (final \ velocity - initial \ velocity)}{Time}$

Force =$\frac{1000(0-30)}{4}$

Force =$\frac{1000(-30)}{4}$

Force =$\frac{-30,000}{4}$

Force = -7500 Newtons

7500 newtons is required to stop the car in the opposite direction of the motion of the car

Answer 2

Answer:

Explanation:

Given :-

Initial velocity of motorcar, u = 108 km/h = 108 × 5/18 = 30 m/s

As 1 km = 1000 m and 1 h = 3600 seconds

Final velocity of motorcar, v = 0 m/s

Mass of motorcar along with passenger, m = 1000 kg

Time taken by motorcar to stops, t = 4 seconds

To Find :-

Force exerted, f = ??

Formula to be used :-

Force = Mass × (Initial velocity - Final velocity)/Time

Solution :-

Putting all the values, we get

Force = Mass × (Initial velocity - Final velocity)/Time

⇒ Force = 1000 × (0 - 30)/4

⇒ Force = 1000 × (- 30)/4

⇒ Force = - 30000/4

⇒ Force = - 7500 Newtons

Hence, the force exerted by the  brakes on the motorcar - 7500 Newtons.