Question

A car is moving with a velocity of 108 km/h. If driver of the car want to change its velocity from108 km/h to 90km/h in two minutes. Mass of the car is 308 kg. What force applied by the brake on the tyres?

Answer 1

-12.83N is force applied

Answer 2

Answer:

A car is moving with a velocity of 108 km/h. If the driver of the car wants to change its velocity from108 km/h to 90km/h in two minutes. The mass of the car is 308 kg. The force applied by the brake on the tyres will be $-12.83\ N$

Explanation:

For calculating force (F) applied, consider Newton's second law of motion Which can be stated as,

$F = ma$     ...(1)    

Where,

m -  the mass of the object

a - acceleration

Acceleration can be obtained by calculating the rate of change of velocity with respect to time.

So,

$a = \frac{v-u}{t}$    ...(2)

Then first equation become,

$F =m( \frac{v-u}{t})$  ...(3)

where

u -  Initial velocity

v -  Final velocity

t  -  Time

From the question,

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

$v = 90\ km/h = 90\times \frac{5}{18} = 25\ m/s$

$m = 5\ kg$

$t = 2m = 2\times 60s = 120\ s$

Substituting these values into equation (3),

$F =308( \frac{25-30}{120}) =-12.83\ N$ ....(4)