A hockey puck slides across the ice at a constant speed. Is it in equilibrium? Why or why not?
Solution 25E Equilibrium is achieved when the total force acting on an object is zero. If there are more than one force acting on the body and the resultant of the force is zero, we can still say that the object is in equilibrium. Since the puck is moving at constant velocity, no horizontal force is acting on the puck (otherwise, the velocity will change). Now on the earth surface, the gravity will always act on the puck, which will be in the downwards direction. But, since, the puck is on the ice, there will be a reaction force acting on the puck by the ice, which will be an upward force. Hence the two force will cancel each other and total force will be zero. Hence, we can say that the hockey puck is in equilibrium.