Question

The velocity-time graph of a body is shown in the given figure. It implies that, over the section B the body experiences

(A) zero force
(B) force towards motion
(C) force opposing motion
(D) only force of gravity

Answer 1

Hint:In order to solve this question, we should know that in a velocity time graph, the slope of straight line gives us the acceleration, and force is directly proportional to the acceleration by newton’s second law so, using this concept we will understand the nature of force acting on the body during the section B as shown in the diagram.




Complete answer:
From Newton's second law we have, $F = ma$ where F denotes force, m is the mass of the body and ‘a’ is the acceleration of the body, so we see that force is directly related with the acceleration of the body. Now, from the given diagram we see that Y axis represents velocity v and X axis represent time t and during section B with increasing time velocity is decreasing or we can say that the slope which is $\dfrac{{dv}}{{dt}}$ will be negative and we know that the ratio of change of velocity with time or slope of velocity and time in v-t graph is acceleration, $a = \dfrac{{dv}}{{dt}}$ and as we know, velocity is decreasing with time so, slope which is acceleration a is negative.

Now, Negative acceleration implies that force acting on the body during section B is also negative as $F = ma$ so, a negative force implies that force is acting in a direction opposite to the direction of the motion of the body which means force is opposing the motion of the body.
So, During the section B from the given velocity-time graph diagram, force is opposing the motion of the body due to negative acceleration acting during that interval.

Hence, the correct option is Option (C).


Note:It should be noted while examining the velocity time graphs that in order to find nature if slope of path we need to check the change in velocity with increasing time and remember the basic formula of slope that slope is ratio of change in quantity represented at Y axis to the quantity represented at X axis.