Which concept explains why objects keep doing what they are doing unless forced to change?

Which concept explains why objects keep doing what they are doing unless forced to change?

• A. Equilibrium
• B. Inertia
• C. Friction
• D. Momentum

Answer: (B)

Inertia is the tendency of matter to resist changes in its motion. An object at rest stays at rest and an object in motion keeps moving in a straight line at constant speed unless a net external force acts to change its motion. Mass is a measure of inertia—the more mass, the greater the resistance to a change in motion. That’s why we say objects keep doing what they’re doing unless something pushes, pulls, or slows them down. For example, a book on a table won’t move unless you push it, and a puck sliding on ice will keep moving until friction or another force slows it. Friction, momentum, and equilibrium relate to motion in different ways, but inertia is the idea that explains why motion or rest tends to continue until an outside force intervenes.

Inertia is the tendency of matter to resist changes in its motion. An object at rest stays at rest and an object in motion keeps moving in a straight line at constant speed unless a net external force acts to change its motion. Mass is a measure of inertia—the more mass, the greater the resistance to a change in motion. That’s why we say objects keep doing what they’re doing unless something pushes, pulls, or slows them down. For example, a book on a table won’t move unless you push it, and a puck sliding on ice will keep moving until friction or another force slows it. Friction, momentum, and equilibrium relate to motion in different ways, but inertia is the idea that explains why motion or rest tends to continue until an outside force intervenes.