Question

Describe a situation in which the net external force on a system is not zero, yet its speed remains constant.

Short answer

Any body moving in a circular path has centripetal acceleration, where the speed of the body remains constant when some external force acts on it.

Step-by-step solution

Defining Newton’s second law of motion

Newton’s second law of motion states that the acceleration of a system is directly proportional to the net external force acting on the system and is inversely proportional to the mass of the system.Mathematically

$F_{net}=ma$

Here,F_net is the net force, m is the mass, and a is the acceleration.

Explanation for situation of nonzero net external force having constant speed

In the situation where a body is moving in a circle with centripetal acceleration, the net external force acts on the body with the speed remaining constant. In this case, the force is applied perpendicular to the direction of velocity, which changes its direction without changing the speed.