2. Objectives

Students will be able to…
 Distinguish the differences among the
sliding, rolling, and liquid friction
 Define friction and what its strength
depends on
 Give real-world examples of and define:
friction, gravity, and weight

4. Friction is…
The force that one surface puts on
another when two surfaces rub against
each other.
 Example: rub your hands together
 It acts in the opposite direction of the
object’s motion.


5. Its Strength Depends on…

1: The types of the two surfaces
involved
 Smooth, bumpy, slippery, etc.

2: How hard the surfaces are being
pushed together

6. Types:

Sliding
 Two solid surfaces rub or slide over each
other

Rolling
 When one object rolls over another solid
surface

Fluid
 When an object moves through a liquid or
gas

8. Gravity is…

The force that pulls objects toward each
other

9. 
Free fall
 The only force acting on an object is gravity
 The object accelerates as it falls

Projectile
 An object that is thrown horizontally
 Also is in free fall

Air Resistance
 Fluid friction, object falls through the air

Terminal Velocity
 A point at which the object does not continue
to accelerate, it reaches its greatest velocity
(speed) at this point
 Because of air resistance and gravity
balancing it

11. Weight is…
The force of gravity on a person or
object at the surface of the planet
 This is not equal to mass:

 Weight = a measure of the force of the
gravity on an object
 Mass = a measure of the amount of matter
in an object

12. Newton’s Laws

Second Law of Motion
 Weight = Mass x Acceleration due to gravity

Law of Universal Gravitation
 Force of gravity acts between all objects in the
universe

13. powerpoint
 Activities
 Worksheet
