Question

a car has a mass 1520 kg is travelling at 20m/s. the driver then applies the brakes and the car comes to a rest in a time of 1.8 s. calculate the deceleration of the car (2 marks)

Answer 1

11.11 m/s²

Explanation:

Given:

• Mass of car, m = 1520 kg
• Initial velocity, u = 20 m/s
• Final velocity, v = 0 m/s (since the car comes to a rest)
• Time, t = 1.8 s

To find:

deceleration(-a) = ?

Solution:

We have a formula of equations of motions:

`\boxed{\boxed{\sf v = u + at }}`

Where

• v = Final velocity
• u = Initial velocity
• a = Acceleration due to gravity
• t = Time

Substituting in the given values and solving for a.

`\sf 0 = 20 + a\cdot 1.8`

`\sf 0 = 20 + 1.8 a`

`\sf 1.8a = - 20`

`\sf a =(-20)/(1.8)`

`\sf a = -11.11\: m/s^2`

If the acceleration is negative than it's called a deceleration.

So,

The deceleration of the car is 11.11 m/s²