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Question

Physics Question on laws of motion

When a car moves on a road with uniform speed of 30km/h30\,km /h, then the net resultant force on the car is

A

the driving force, drives the car in the direction of propagation of car

B

the resistive force acts opposite to the direction of propagation of car

C

zero

D

None of the above

Answer

zero

Explanation

Solution

Force on a body is the product of its mass and acceleration produced.
Force == mass ×\times acceleration
From Newton's second law of motion, the force (F)(F) acting on a body moving with constant velocity (v)(v) is given by
F=F= mass ×\times acceleration
We know that acceleration =dvdt=\frac{d v}{d t}
Fdvdt\therefore F \propto \frac{d v}{d t}
Given, v=30km/hv=30 \,km / h
Fddt(30)F \propto \frac{d}{d t}(30)
F=0F=0
Alternative :The external force on the body always produces some acceleration in the object. This implies there is a variable speed. As speed of car (object) is uniform, so there will be no net force on the car.