Laws of Motion — Important Questions

Displacement, Velocity, Acceleration

Vector quantities have both magnitude and direction. Displacement, velocity, and acceleration are vectors. Distance, speed, and time are scalar quantities with only magnitude.

Walking on ground, Recoil of gun, Rocket propulsion, Swimming

All involve action-reaction pairs: foot pushes ground/ground pushes foot; bullet forward/gun backward; exhaust gases down/rocket up; hands push water back/water pushes body forward. Free fall involves only gravity.

p = mv

Momentum is defined as the product of mass and velocity (p = mv). ma gives force, not momentum. The other options are incorrect relationships.

Speed

In uniform circular motion, speed remains constant but velocity changes due to continuous change in direction. Acceleration is present due to changing velocity.