1. Force
A Push or a Pull

2. A Push or a Pull A force is a push or a pull.
Force is measured in newtons (N)
You exert about 1 N of force when you lift a lemon
Often more than one force is acting upon an object at one time. The combination of all forces acting on an object is called net force.
The net force determines if an object moves and in what direction.

3. Net Force

4. Unbalanced and Balanced Forces
Unbalanced forces acting on an object result in a net force and cause a change in the objects direction.
Balanced forces acting on an object do not change the object’s motion.

5. Friction
Friction is the force that two surfaces exert on each other when they rub against each other.
The strength of the force depends on two factors
How hard the surfaces are
The types of surfaces involved

6. Types of Friction Static Friction Sliding Friction Rolling Friction
Friction that acts upon objects that are not moving, it opposes the intended motion
Sliding Friction
When two solid surfaces slide over each other
Rolling Friction
When an object rolls over a solid surface
Fluid Friction
When a solid object moves through a fluid

7. Which is Which?

8. Gravity
Sir Isaac Newton concluded that a force acts to pull objects straight down to the center of the Earth.
gravity is the force that pulls objects together
Newton realized that the force of gravity acts between all objects in the universe
This is called the law of universal gravity.

9. Gravity
Two factors affect the gravitational attraction between objects:
Mass-the amount of matter in an object (kg)
The more mass, the greater its gravitational pull
Distance
The further apart, the less gravitational pull

10. Weight and Mass Mass is sometimes confused with weight
Mass is the amount of matter in an object
Weight is a measure of the gravitational force exerted on an object
Weight varies depending on the strength of the gravitational force, while mass does not change
Did you know…you weigh less on the moon than you do on Earth?

11. Gravity and Motion
When gravity is the only force acting on an object it is in free fall
Objects falling through air experience a type of fluid friction called air resistance.
It is the upward force exerted on falling objects

12. Projectile Motion An object that is thrown is called a projectile.
Does it hit the ground at the same time as an object that was dropped?????