alleryA force F acts on a particle making an angle θ with its instantaneous velocity. The component of velocity perpendicular to F:
AIncreases with time at the rate F sinθ / m
BDecreases with time at the rate F cosθ / m
CRemains unchanged
DBecomes zero after one cycle
Answer & Solution
Correct answer: C. Remains unchanged
1. The second law is a vector law: each force component changes only the corresponding velocity component.
2. The component of velocity normal to F has zero force component along it.
3. With no acceleration along that direction, the normal velocity component is unchanged.
4. This is why the horizontal velocity of a projectile under gravity stays constant.
_Source: syllabus Physics Ch 4 "Laws of Motion", §4.5 (point 2 on second law), p. 55_
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