Question

If a body is moving with a constant speed along a straight line; then in order to change its direction of motion, an external force has to be applied in a direction normal to the direction of motion.

• A. True
• B. False

Answer 1

The correct option is B False

Newton's First law of motion - "Every body continues to be in its state of rest or of uniform motion in a straight line unless compelled by some external force to act otherwise".

According to Newton's First law of motion, first half of the statement is true, an external force has to be applied. But "in a direction normal to the direction of motion" is false. The applied force doesn't have to be always normal to the direction of motion to change its direction of motion. For example, a bat hitting a ball applies a force in a direction opposite to its motion and yet it can change its direction of motion.