2023 Motion in a PlaneVectors – Change in Velocity Medium Question 2 of 56 in Motion in a Plane

A football player is moving southward and suddenly turns eastward with the same speed to avoid an opponent. The force that acts on the player while turning is:

A along south-west
B along eastward
C along northward
D along north-east

The answer is D.

Solution

Change in velocity points north-east, so the force is along north-east.

Initial velocity $=-v\hat{j}$, final velocity $=v\hat{i}$ Change in velocity $=v\hat{i}-(-v\hat{j})=v(\hat{i}+\hat{j})$ Momentum gain is along $\hat{i}+\hat{j}$ $\Rightarrow$ force experienced is along $\hat{i}+\hat{j}$ $\Rightarrow$ force experienced is in North-East direction.

Concept direction of force from change in velocity

Motion in a Plane in past papers

56 questions from this chapter have appeared across 22 exam years.