Question

Which motion does not require force to maintain it?

• A. Uniform circular motion
• B. Elliptical motion
• C. Uniform straight line motion
• D. Projectile motion

Answer 1

Answer: (C)

Uniform straight line motion

Answer 2

According to Newton's second law of motion $F = ma$ When body is moving uniformly along a straight line and there is no force of friction, acceleration/retardation of the body $a= 0.$ $\therefore F = m$ $a = 0$ ie, no external force is required. For accelerated motion, force is necessary. In uniform circular motion, elliptical motion and projectile motion direction of velocity changes due to which force is imposed.