Question

A 2500 kg car is moving at 20 m/s when brakes are applied. If the average force exerted by the brakes

is 5000 N, find the distance travelled by the car before it comes to rest? ​

Answer 1

Given :-

• Mass of the car = 2500 kg
• Initial velocity of the car = 20 m /s
• Final velocity = 0 m/s ( breaks applied )
• Force exerted = - 5000 N ( negative sign indicates that the force is retarding )

To find :-

• Distance traveled by the car

How to solve :-

• First we need to find the acceleration of the car by applying Newton's second law of motion
• As the car is moving with uniform acceleration throughout it's motion we can use the third or second kinematic equation to solve this question

Solution :-

By applying Newton's second law of motion

⟹ F = ma

here ,

• F = force
• m = mass
• a = acceleration

⟹ a = - 5000 / 2500

⟹ a = - 2 m/s²

Now that we have a let's apply first kinematic equation to get the distance (s )

⟹ v² = u ²+ 2as

here ,

• v = final velocity
• u = initial velocity
• a = acceleration
• s = distance

⟹ 0 = 400 - 2 x 2 x s

⟹ s = 400 / 4

⟹ s = 100 m

The distance traveled by the car is 100 m