A delivery van sits parked. A car with cruise control on passes it, holding a steady velocity on a straight, flat road. Two very different motions.
One thing is the same for both: the net force. What is that shared state called?
Check the parked van first. Its weight and the normal force from the road balance, so the net force on it is zero.
Now check the cruising car. Its velocity is constant, and by Newton's first law a constant velocity is the sign that the forces on it cancel. The net force on it is zero too.
By Newton's first law, each keeps its velocity: the van stays at rest, and the car holds its steady velocity.
The two cases share a name. When the net force on an object is zero, the object is in translational equilibrium.
Translational means to do with moving from place to place. This course deals only with that kind, so we will say equilibrium for short.
The net force on a railroad boxcar is zero. Which statement is correct?
Equilibrium covers both cases: at rest, or moving at constant velocity. Equilibrium does not mean at rest. The cruising car is in equilibrium while it moves.
A subway car moves at a constant velocity on a straight track. Is it in equilibrium?
The test is one question: is the net force zero?
A dog sled moves at constant velocity across flat snow. Is it in equilibrium, and what is the net force on it?
Its velocity is constant.
By Newton's first law, a constant velocity means the net force is zero.
Zero net force is the definition of equilibrium.
Yes: it is in equilibrium, and the net force on it is 0 N.
A gym bag lies at rest on a bench. Is it in equilibrium?
At rest is a constant velocity of zero.
The bag keeps that velocity, so the net force on it is zero.
Yes: at rest on the bench, the bag is in equilibrium.
Which object is in equilibrium?
A canoe is in equilibrium. Which statement must be true?
A tour bus holds a steady 24 m/s along a straight, flat highway. Enter the net force on it in N.
Type the name for the state of an object when the net force on it is zero.