Arizona State University (ASU) PHY101 Introduction to Physics Practice Exam

To understand why the statement that all pucks require the same force to keep them moving is correct, it is essential to consider Newton's First Law of Motion, which states that an object in motion will remain in motion with a constant velocity unless acted upon by a net external force. This implies that, once the pucks are sliding across the ice at their respective speeds, they will continue to do so as long as no additional forces (like friction or air resistance) act on them.

In this scenario, if the pucks are already sliding and moving at constant speeds of 2 m/s, 4 m/s, and 6 m/s, they do not require a force to maintain their motion. The distinction lies in the understanding that while forces may be necessary to change the speed or direction of the pucks, once they are already in motion, they can continue moving without any ongoing force. Each puck, regardless of its speed, is in a state of constant velocity and thus experiences no net force required to maintain that state.

Therefore, since none of the pucks needs any additional force to keep moving at their respective speeds, the conclusion that all require the same force – which is effectively zero – is accurate.