Newton first law notes

What is Newton's First Law?

An object at rest stays at rest, and an object in motion stays in motion unless acted upon by a net external force.

Define inertia.

Inertia is the resistance of any physical object to any change in its velocity, including a change to the object's speed or direction.

True or false: Forces are always needed to maintain motion.

False, because objects in motion can continue moving without forces if no net external force acts on them.

Difference between mass and weight.

Mass is the amount of matter in an object, while weight is the force of gravity acting on that mass ($\displaystyle W = mg$).

Fill in the blank: An object in motion will continue in motion at a constant velocity until ___ .

it is acted upon by a net external force.

What does 'net external force' mean?

The overall force acting on an object, considering all individual forces applied to it.

Question: What is an example of inertia?

A book resting on a table will remain at rest until someone picks it up.

True or false: A bus in motion will eventually stop without external forces.

True, because friction and air resistance are external forces that slow it down.

List two effects of unbalanced forces.

1. Change in velocity. 2. Change in direction.

What happens to a rolling ball on a smooth surface?

It continues rolling at a constant speed and direction if no external forces like friction act on it.

Question: How does mass affect inertia?

Greater mass means greater inertia, requiring more force to change its state of motion.

True or false: A car can stop instantly without any forces acting.

False, because it requires a braking force to stop.

Fill in the blank: An object at rest remains at rest until a ___ acts on it.

net external force.