Forces

1
Forces

• MYP / Honors Physics

2
Facts about FORCE

• Unit is the NEWTON(N)
• Is by definition a push or a pull
• Can exist during physical contact(Tension,
  Friction, Applied Force)
• Can exist with NO physical contact, called FIELD
  FORCES ( gravitational, electric, etc)

3
When forces act on an object they are said to be
balanced or unbalanced.
Balanced Forces are equal in magnitude AND
opposite in direction.
5 N
5 N
10 N
10 N
10 N
10 N
5 N
5 N
When balanced forces act on an object the
resultant is always
zero.
When balanced force act, the object is in a state
of equilibrium.
4
Q What is the magnitude of the unknown force
that will cause equilibrium?
25 N
? N
25 N
? N
15 N
25 N

1. 15 N
2. 40 N
3. 10 N
4. 0 N

1. 25 N
2. 50 N
3. 35 N
4. 0 N

5
What effect will balanced forces have on the
motion of an object?
NONE!
When balanced forces act on an object, there is
no change in the motion of the object.
6
Unbalanced Forces are not equal in magnitude OR
not opposite in direction.
5 N
5 N
10 N
3 N
5 N
4 N

• QWhat is the resultant force?
• 15 N
• -5 N
• 5 N
• -15 N

• QWhat is the resultant force?
• 5 N
• 0 N
• -5 N
• 10 N

• QWhat is the magnitude of the resultant force?
• 5 N
• 7 N
• 1 N
• -1 N

When unbalanced forces act on an object the
resultant is always
nonzero.
This resultant force is called the net force.
7
What effect will unbalanced forces have on the
motion of an object?
Motion will change!

• How could the motion change?
• speed up
• slow down
• change direction

What one word describes all three of theses
changes?
Acceleration!
An net force will cause a mass to accelerate.