Question

what is required to change the motion of an object according to newtons 1st law?
a. a net external force.
b. no force is needed.
c. friction must be applied.
d. gravity must act on it.

Explanation:

Newton's 1st law states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by a net external force. So a net external force is required to change the motion of an object. Friction and gravity are types of forces but not the only ones that can change motion, and no - force will keep the object in its current state of motion.

Answer:

A. A net external force.