Page 21 - Science Course 2 (Book 2)

Mo8-L2a: What is Newton’s First Law of Motion?

Newton’s f rst law of motion only applies to balanced
forces acting on an object.

When unbalanced forces act on an object, the object’s
velocity changes.

The marble speed up
rolling down the ramp

The tendency of an object to stay at rest

The marble slows down Key Concept
rolling up the ramp.
What is Newton’s First Law of Motion?

What effect does inertia have on the motion of an
The marble will neither slow object?
down nor speed up rolling on
a perfectly horizontal surface.

Key Concept

What is Newton’s First Law of Motion?
How is motion related to balanced and unbalanced
forces?

Why Do Objects Stop Moving

For an object to start moving, a
force greater than static friction
must be applied to it.

To keep an object in motion, a
force at least as strong as
friction must be applied
continuously.

Objects stop moving because
Inertia friction or another force acts
on them.
The tendency of an object to resist a change in its
motion is called inertia.

SUMMARY
What is Newton’s First Law of Motion?
Unbalanced forces cause an object to move.

According to Newton’s f rst law of motion, if
the net force on an object is zero, the object’s
velocity does not change.

The tendency preserve its state of motion. Inertia is a property that resists a change in the
motion of an object.
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