Question

A car travels at a speed of 60 kph then slows down to 45 kph in 10 seconds. What is the acceleration of the car?

Answer 1

Given:

A car travels at a speed of 60 kph then slows down to 45 kph in 10 seconds.

To find:

Acceleration of the car?

Calculation:

Acceleration is often defined as the instantaneous rate of change of velocity with respect to time.

Now , converting unit of speed from km/hr to m/s:

$1) \: 60 \: km/hr = 60 \times \dfrac{5}{18} = 16.67 \: m/s$

$2) \: 45\: km/hr = 45 \times \dfrac{5}{18} = 12.5 \: m/s$

Now , considering acceleration to be constant and applying the 1st equation of kinematics:

$\therefore \: v = u + at$

$= > \: 12.5= 16.67+ at$

$= > \: 12.5= 16.67+ a(10)$

$= > \: 10a = - 4.17$

$= > \: a = - 0.417 \: m/ {s}^{2}$

So, acceleration is -0.417 m/s².

• Negative sign of acceleration denotes retardation or deceleration of the car.

Hope It Helps.