When a car moves on a road with uniform speed of $30\,km /h$, 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
The Correct Option is C
Solution and Explanation
Force $=$ mass $\times$ 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 $\times$ acceleration
We know that acceleration $=\frac{d v}{d t}$
$\therefore F \propto \frac{d v}{d t}$
Given, $v=30 \,km / h $
$F \propto \frac{d}{d t}(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.
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Concepts Used:
Laws of Motion
The laws of motion, which are the keystone of classical mechanics, are three statements that defined the relationships between the forces acting on a body and its motion. They were first disclosed by English physicist and mathematician Isaac Newton.
Newton’s First Law of Motion
Newton’s 1st law states that a body at rest or uniform motion will continue to be at rest or uniform motion until and unless a net external force acts on it.
Newton’s Second Law of Motion
Newton's 2nd law of motion deals with the relation between force and acceleration. According to the second law of motion, the acceleration of an object as built by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
Newton’s Third Law of Motion
Newton's 3rd law of motion states when a body applies a force on another body that there is an equal and opposite reaction for every action.