1. Mr. Capo
Force

2. Force – push or pull
A force always acts in a certain direction (Examples)
ex. if you push something, the force is in the direction of the push
Classroom door
Kicking Ball

3. Forces in Nature Electric force Magnetic force Gravity ex. lightning
ex. magnetic poles
Gravity

4. Is weight is a force ?

5. Newton
Metric unit of force

6. What is gravity?
Sir Isaac Newton
1642 – 1727
The Principia

7. Gravity
Force of attraction between all objects in the universe

8. Gravity
The larger an object’s mass, the greater the gravitational force

9. Gravity
The greater the distance between two objects, the smaller the gravitational force
the force of gravity decreases by the amount equal to one divided by the distance (d) squared
1/d2

10. What is air resistance? air resistance
force that opposes the movement of an object in air

11. Air Resistance
a larger surface area usually results in greater air resistance
lighter objects feel more air resistance than heavier objects

12. Terminal Velocity
speed at which air resistance and gravity acting on an object are equal
as an object falls, it’s speed increases at a steady rate until it reaches it’s terminal velocity

13. Vacuum – empty space
in a vacuum, all objects fall at the same speed

14. What is friction? Friction force that opposes the motion of an object
the force of friction works in the opposite direction of the force of motion

15. Types of Friction Sliding Friction
the source of friction is the contact between two surfaces, at least one of which is in motion

16. Types of Friction Air Resistance
friction results from air pushing on an object as it is moving

17. Types of Friction Rolling Friction
friction between two surfaces that are not in constant contact
ex. wheels

18. Friction friction makes motion possible
friction also makes it hard to move objects
reducing friction makes it easier to move objects

19. How can friction be reduced?
by changing sliding friction into rolling friction
by using lubricants
Lubricants – substances that reduce friction

20. What is pressure?
Pressure
force per unit area

21. Pressure pressure is the amount of force acting on a surface
pressure equals force divided by area
p = f/a

22. Pressure
pressure can be changed by changing the amount of force acting on an area
pressure can be changed by changing the area on which a force acts

23. Fluid Pressure
pressure in gases and liquids

24. Air Pressure
air pressure is caused by the motion of particles in the air
you do not feel the weight of the air because the pressure inside your body is equal to the air pressure around you

25. Air Pressure air pressure changes with altitude
the higher you are, the lower the air pressure

26. Air Pressure
Barometer
instrument used to measure air pressure

27. Water Pressure
the force of water pressure on an object is the same in all directions
water pressure changes with depth
the deeper you are, the greater the water pressure

28. Water Pressure Manometer
instrument used to measure pressure in a liquid

29. What is Bernoulli’s principle?
principle that states that as the speed of a fluid increases, its pressure decreases

30. Bernoulli’s Principle
airplane wings are designed to use Bernoulli’s principle
air traveling over the wings moves faster than air underneath
this reduces the pressure on top of the wing, allowing it to be pushed upward

31. Bernoulli’s Principle
three forces combine to help an airplane fly
the upward force on a plane’s wing is called lift
a forward force, or thrust, helps the plane take off and maintain air speed
the air resistance on a plane is called drag