Which situation describes an object that has no
unbalanced force acting on it?
(1) an apple in free fall
(2) a satellite orbiting Earth
(3) a hockey puck moving at constant velocity
across ice
(4) a laboratory cart moving down a frictionless
30.° incline



Answer :

"(3) a hockey puck moving at constant velocity across ice" is the best option from the list but it should be noted that it is impossible to have truly frictionless ice. 

The answer is:

3) a hockey puck moving at constant velocity across ice.

The explanation:

when the Balanced forces do not cause a change in motion. When balanced forces act on an object at rest, the object will not move. If you push against a wall, the wall pushes back with an equal but opposite force. Neither you nor the wall will move. Forces that cause a change in the motion of an object are unbalanced forces.  

- A force which is not opposed by a force of equal magnitude and acting in the exact opposite direction hence leading to the motion of the object is called an unbalanced force.

- The forces which speed up slow down the objects or makes them change their direction are called Unbalanced forces.

and the phase which satisfy this definition is (3)