Clara gets an empty shopping cart moving: easy to start, easy to stop. Then she loads it with heavy bags of salt. Now the same cart is hard to get moving, and once it is moving, it is hard to stop.
What changed about the cart?
Every object tends to keep its current velocity. An object at rest tends to stay at rest. Both carts do that. A moving object tends to keep moving at the same speed, in the same direction.
Velocity means speed in a stated direction, so keeping a velocity means keeping both. The tendency resists turning, too.
This tendency is called inertia.
Objects differ in how strong the tendency is. The measure is mass.
The loaded cart has more mass than the empty cart, so it has more inertia. More inertia is what made the loaded cart harder to start, harder to stop, and harder to turn.
A loaded freight car and an empty freight car roll along a track at the same speed. Which is harder to stop?
Which quantity measures an object's inertia?
Inertia is not a force. No second object exerts anything. It is a tendency the object itself has.
A loaded moving van and an empty one roll side by side at the same velocity. Which van is harder to stop, and why?
Both vans tend to keep their current velocity: that tendency is inertia.
Mass measures inertia, and the loaded van has more mass.
So the loaded van resists the change more.
The loaded van is harder to stop: more mass, so more inertia.
A 6 kg medicine ball and a 0.6 kg playground ball roll toward Yusuf at the same velocity. Which is harder to turn aside, and why?
Turning changes the direction, and direction is part of velocity.
Inertia resists every change of velocity, and mass measures it.
The medicine ball has ten times the mass.
The medicine ball: more mass, so more inertia, so more resistance to the turn.
A 1200 kg car and a 300 kg go-kart coast side by side at the same velocity. Which statement is correct?
A bowling ball and a soccer ball sit at rest on a rack. Which is harder to get moving?
Which statement uses inertia correctly?
Type the name for an object's tendency to keep its current velocity.