Question
Physics Question on laws of motion
When a car moves on a road with uniform speed of 30km/h, then the net resultant force on the car is
the driving force, drives the car in the direction of propagation of car
the resistive force acts opposite to the direction of propagation of car
zero
None of the above
zero
Solution
Force on a body is the product of its mass and acceleration produced.
Force = mass × acceleration
From Newton's second law of motion, the force (F) acting on a body moving with constant velocity (v) is given by
F= mass × acceleration
We know that acceleration =dtdv
∴F∝dtdv
Given, v=30km/h
F∝dtd(30)
F=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.