Solved: PHYSICS Question for NEET

NEET PHYSICSMedium

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:

along south-west

along eastward

along northward

along north-east

Step-by-Step Solution

Identify the Principle: According to Newton's Second Law of Motion, the net force ( $\\mathbf{F}$ ) acting on an object is proportional to the rate of change of momentum ( $d\\mathbf{p}/dt$ ). Since mass is constant, the direction of force is the same as the direction of the change in velocity ( $\\Delta \\mathbf{v}$ ). $\\mathbf{F} \\propto \\Delta \\mathbf{p} = m(\\mathbf{v}_f - \\mathbf{v}_i)$
Analyze Vectors:

Initial Velocity ( $\\mathbf{v}_i$ ): Southward.
Final Velocity ( $\\mathbf{v}_f$ ): Eastward.
Change in Velocity ( $\\Delta \\mathbf{v}$ ): $\\mathbf{v}_f - \\mathbf{v}_i = \\mathbf{v}_f + (-\\mathbf{v}_i)$ .

Determine Direction:

The vector $-\\mathbf{v}_i$ points North (opposite to South).
The vector $\\mathbf{v}_f$ points East.
The resultant of a Northward vector and an Eastward vector acts along the North-East direction.

Conclusion: The force responsible for the turn (friction) acts along the North-East direction. (Reference: NCERT Class 11, Physics Part I, Chapter 4: Motion in a Plane, Section 4.7-4.9 discusses vector subtraction; Chapter 5: Laws of Motion, Section 5.5 discusses force and momentum change [1]).

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