NDA 2 2024 GAT, question 96

Topic: Physics

Q96

A car weighs $1000\text{ kg}$ . It is moving with a uniform velocity of $72\text{ km/h}$ towards a straight road. The driver suddenly presses the brakes. The car stops in $0.2\text{ s}$ . The retarding force applied on the car to stop it is

(a) $100\text{ N}$
(b) $1000\text{ N}$
(c) $10\text{ kN}$
(d) $100\text{ kN}$ Correct answer

Solution.

Answer: (d) $100\text{ kN}$

Convert 72 km h⁻¹ to 20 m s⁻¹.
The deceleration magnitude is (20−0)/0.2=100 m s⁻².
With mass 1000 kg, force magnitude=ma=100000 N=100 kN.
The source's kilogram value denotes mass, not weight in newtons.