Question

a hockey puck slides on ice at a constant velocity. how does newtons first law explain why it keeps moving with little change in speed?
the puck is very light, so it has no inertia.
ice has very little friction, so there is almost no unbalanced force to slow the puck down, and its inertia keeps it moving.
the cold temperature of the ice creates a force that propels the puck forward.
the force from the hockey stick is still pushing it.

Explanation:

Newton's First Law states that an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. In this case, the ice has very little friction, so there is almost no unbalanced force to slow the puck down. The puck's inertia (its tendency to resist changes in motion) keeps it moving.

• The first option is incorrect because all objects have inertia, regardless of their weight.
• The third option is incorrect because temperature does not create a force that propels the puck forward.
• The fourth option is incorrect because the force from the hockey stick is no longer acting on the puck once it is sliding on the ice.

Answer:

The second option: Ice has very little friction, so there is almost no unbalanced force to slow the puck down, and its inertia keeps it moving.