1. Chapter 2: The Laws of Motion

3. What do you think? Agree or Disagree?

4. Lesson 1: Gravity and Friction

5. Force STRENGTH DIRECTION STOP MOVING START MOVING CHANGE DIRECTION
A push or pull on an object.
Described by:
A force gives an object energy to:
STRENGTH
DIRECTION
STOP MOVING
START MOVING
CHANGE DIRECTION

6. Types of Force
Contact Force
Non Contact Force

7. Contact and Noncontact Sports
How do these relate to the title of this lesson? (Gravity and Friction?)
Contact = friction
Noncontact = gravity

8. Contact Force
A push or pull on one object by another that is touching it.
Contact forces can be:
Strong OR
Weak

9. Noncontact Force
A force that one object can apply to another object without touching it.
Examples Include:
Gravity
Magnetic Force
Electric Force

10. Strength and Direction of Forces
can be used to show forces.
The of an arrow shows the
of the force.
The that the arrow points shows the direction in which the
The stronger the force the the arrow.
ARROWS
LENGTH
STRENGTH
DIRECTION
FORCE WAS APPLIED
LONGER

11. Strength and Direction of Forces
The SI unit for force is the
The symbol for Newton is
One Newton = about the force you exert to lift a lime.
Named after:
NEWTON N
Sir Isaac Newton (founder of physics)

12. Gravity Force of gravity
An attractive force that exists between all objects that have mass.
Force of gravity
On EARTH the force of gravity = 9.8 m/s2
All objects fall to the Earth at an acceleration of 9.8m/s2 due to the force of gravity.

13. The Law of Universal Gravitation
Sir Isaac Newton (1600’s)
The law states:
Factors Affecting Gravity
All objects are attracted to each other by a gravitational force. The strength of force depends on the MASS of each object and the DISTANCE between them.
MASS
DISTANCE

14. Mass
The amount of matter in an object.
Which object has more mass?

15. Gravitational Force and MASS
When the mass of one or both objects
the gravitational force between them also
Regardless of the amount of mass an object has the will be the
Each object exerts the attraction on the other object.
INCREASES
INCREASES
FORCE ARROWS
SAME SIZE
SAME

17. Gravitational force and DISTANCE
The attraction between objects
as the between the object
DECREASES
INCREASES
DISTANCE

18. Weight The gravitational force exerted on an object.
Weight is measured in
Near Earth’s surface the object’s weight is the
NEWTONS
FORCE DUE TO GRAVITY

19. Weight and Mass on Earth
Weight and mass are related, but ARE NOT the same.
Weight can due to
Mass change
FORCE =
CHANGE
GRAVITY
DOES NOT
MASS x ACCELERATION
F =
Weight on Earth =
M x A
MASS x 9.8m/s2 (acceleration due to the force of gravity)

20. Examples: What would an object with a mass of 10 kg weigh?
If your mass was 50kg, what would your weight be?

21. Net Force The combination of all the forces acting on an object.
To calculate the net force:
If the forces act in the same direction they are added together.
If forces act in opposite directions they are subtracted.

22. Combining Forces - Unbalanced
Forces acting on an object that combine and form a net force that is not zero.
Unbalanced forces cause an object to move.
Forces moving in the same direction are
Forces moving in the opposite direction are
ADDED
SUBTRACTED

23. Combining Forces – Balanced Forces
Forces acting on an object that combine and form a net force of ZERO. NO change in motion.

24. Friction STATIC FRICTION SLIDING FRICTION FLUID FRICTION
A force that resists the motion of two surfaces that are touching.
Types of friction
STATIC FRICTION
SLIDING FRICTION
FLUID FRICTION

25. Static Friction
Friction that acts
on objects that
are not moving.

26. Sliding Friction
When solid objects
slide over each other.

27. Fluid Friction SHAPE SIZE MASS
A force produced by a fluid (gases or liquids)
Examples: engine oil, grease
Air resistance
Air resistance is affected by:
*objects with more surface area have more air resistance**
a type of fluid friction
Upward force exerted on falling objects.
SHAPE
SIZE
MASS

28. What causes friction? 2 causes of friction
When microscopic dips and bumps that cover surfaces slide past another surface with dips and bumps they catch on to one another.
When a positive charge slides by a negative charge attraction occurs.