Question

A car of mass 1.5 metric ton moving at 22.4 mile/h is brought to rest after it covered a distance of 10 m. Find the retarding force acting on the car, give your final answer in SI units. Marks 8

Answer 1

Given:

A car of mass 1.5 metric ton moving at 22.4 miles/h is brought to rest after it cover the distance of 10 metre.

To find:

Retarding force in SI unit (i.e. Newtown)

Calculation:

We need to first convert all the units to SI units.

For mass:

1.5 metric ton = 1.5 × 1000 = 1500 kg

For velocity:

22.4 mile/hr = 22.4 × 1.6 = 35.84 km/hr

Again, 35.84 km/hr = 35.84 × (5/18)

=> 35.84 km/hr = 9.95 m/s

APPLYING 3RD EQUATION OF KINEMATICS:

$\therefore \: {v}^{2} = {u}^{2} + 2as$

$= > {0}^{2} = {(9.95)}^{2} + (2 \times a \times 10)$

$= > 20a = - 99.0025$

$= > a = - 4.95 \: m {s}^{ - 2}$

Negative acceleration refers to opposite direction with respect to velocity :

So final answer :

Acceleration in SI units is 4.95 m/s²