Question

How much work is required to stop a car of mass 1100 kg that is traveling at 27 m/s? 15kJ
30kJ
40 J
401 kJ

Answer 1

Answer:

Work done, W = 401 kJ

Explanation:

It is given that,

Mass of the car, m = 1100 kg

Initial, velocity of the car, u = 27 m/s

Finally it stops, v = 0

According to work energy theorem, the change in kinetic energy is equal to the work done i.e.

$W=\dfrac{1}{2}m(v^2-u^2)$

$W=\dfrac{1}{2}\times 1100\ kg\times (0-(27\ m/s)^2)$

W = -400950 J

or

$W=-401\ kJ$

-ve sign shows the direction of force and displacement are in opposite direction.

So, 401 kJ work is required to stop a car. Hence, this is the required solution.