Force• A force is a push or a

pull.• The combination of all the forces acting on an object is the net force.

PUSH PULL

Force• Two or more forces exerted on an object are balanced forces if

their effects cancel each other and they do not change the object’s

velocity.• If the forces on an object are balanced, the net force is zero.

Force====

Force

• If the net force is not zero, the forces are unbalanced forces.

Then the effects of the forces don’t cancel, and

the object’s velocity changes.

Force

Draw an example of both balanced and unbalanced forces on your paper.

Gravity

• Gravity is the force of attraction between all

masses in the universe.

Gravity• Depends on the mass of

the objects and the distance between them. • The gravitational force

becomes weaker the farther apart the

objects are and also decreases as the

masses of the objects involved decrease.

Weight• The weight of an object

is the size of the gravitational force

exerted on an object.

Friction• The force that brings nearly everything to a

stop is friction, which is the force that acts to resist sliding between

two touching surfaces.

Friction• Although several

different forms of friction exist, they all

have one thing in common. If two objects are in contact, frictional

forces try to prevent one object from sliding

on the other object.

Static Friction

• The type of friction that prevents an object from moving when a force is applied is called static

friction.

Sliding Friction

• Sliding friction slows

down an object that

slides.

Rolling Friction

• Rolling friction occurs when an object rolls

across a surface.