Page 20 - Science Course 2 (Book 2)

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

Let’s Begin When forces act in opposite direction on an object,
the net force is still the sum of the forces.

Identifying Forces The net force is the sum of the positive and negative
forces.
The sum of all the forces acting on an object is the Balanced forces are forces that combine and form
net force.
a net force of zero.
The net force depends on the directions of the Forces that combine and form a net force that is not
forces applied to an object.
zero are unbalanced forces.
Because forces have direction, you have to specify a
reference direction when you add forces.
+ = 0 Net
Force
200N + –200N = 0N

F2 = 18 Newtons F1 = –20 Newtons Newton’s First Law of Motion

According to Newton’s f rst law of motion, if the net
force on an object is zero, an object at rest will stay
at rest, and a moving object will continue moving in a
straight line with constant speed.

Net Force = –2 Newtons

A force moving in the reference direction is positive,
and a force in the opposite direction is negative.

When the forces applied to an object act in the same
direction, the net force is the sum of the individual
forces.

As a result, balanced forces and unbalanced forces
have different results when they act on an object.

Key Concept

What is Newton’s First Law of Motion?

What is Newton’s f rst law of motion?

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