1. Force, Mass and Motion
S8P3 Students will investigate the relationship between force, mass and motion.
Determine the relationship between velocity and acceleration.
Determine the effect of balanced and unbalanced forces on an object in terms of gravity, inertia, and friction.
Demonstrate the effect of simple machines on work.

2. Vocabulary
Acceleration – the rate at which velocity changes. (speed or direction changes = acceleration)
Acceleration =
Example – Turn left onto another road or going down a hill in a car.
Negative Acceleration – acceleration in which velocity decreases
Example – when a car slows down
Deceleration - acceleration in which velocity decreases
Example – when a plane slows down to land
Final velocity – starting velocity
= m/s/s
Time

3. Vocabulary Speed – rate at which an object moves (distance/time) (m/s)
Example – how fast a ball is thrown, car drives
Velocity – the speed of an object in a particular direction. (distance/time, direction)
Example – The car is driving 5 miles/hour north.
Final Velocity – final point at which velocity is measured
Example – when a car stops or passes an ending point.
Initial Velocity – beginning point at which velocity is measured.
Example – When a car starts or passes a beginning point.

4. Vocabulary
Force – a push or pull. It has size and direction. (Newton (N))
Example – pull open a door, pushing a car door shut.
Mass – the amount of matter in an object. (grams (g))
Example – ping pong ball verses a marble
Motion – when an object changes position over time when compared with a reference point.
Example – running

5. Vocabulary
Friction – a force that opposes motion between two surfaces that are touching.
Rubbing hands together, pushing a box on concrete
Inertia – tendency of all objects to resist any change in motion.
Example – ball will stay in motion unless another force acts upon it like gravity.
Gravity – a force of attraction between objects that is due their masses.
Example – ball falls to the ground.
Distance – the amount of space between two points.
Example – my house is 2 miles from your house

6. Speed
How Fast????
Have to know Distance an object moves and Time needed to travel that distance
Formula
Average Speed = Distance Traveled
meters/second
Time Traveled

7. More about speed
Most objects CONSTANTLY change speed, so when you use the formula, it is the average speed.
If you drive to school, how often do you go 50 mph the entire way? Never.

8. Velocity Speed of an object in a certain direction
2 cars were traveling at 50 km/sec on the highway for 2 hours. After 2 hours, one car was in Alabama and one car was in Florida. HOW???
Opposite Directions! This is why know the direction is important when calculating velocity.

9. More on Velocity It changes when speed OR direction changes
You go from 20 mph to 50 mph, you change velocity
You go from 20 mph to 20 mph, but turn left you changed velocity.
50 mph North shows velocity Why?

10. Acceleration
The rate at which velocity changes, so… speed or direction have to change for the acceleration to change.
Deceleration: slow down
Change in speed or direction = (Final V – Initial V / Time)
Another word for Initial velocity is starting or original.

11. Examine the table below for the acceleration of a car
Examine the table below for the acceleration of a car. You can see the acceleration of the car at any time is 5 m/s/s, so every second, the velocity of the car increases by 5 m/s.
Time (second)
Velocity (meters per second) 1 5 2 10 3 15 4 20

12. TOTD Give one example of a change in acceleration
What info do you need to calculate velocity? (3 things)
What is the average speed of an object that travels over 100 meters in 20 seconds?

13. Inertia
Objects resist change in motion. If I am standing still, I will stay that way until…. This is called INERTIA Inertia is wearing a seat belt Example: a car is going 50 mph and comes to a sudden stop, you continue moving a 50 mph, unless something stops you… a seat belt or the dashboard.

14. Mass VS Inertia
An object with a large mass has more interia. Changing the motion of an object with a large mass is harder than changing the motion of a smaller object. Which would you rather change the motion of?
Moving Car or Rolling Soccer Ball

15. Think about it??? Which would you rather stop falling with your head?
Ping pong ball or marble
Which would you rather pull?
Tractor or wagon
Which would you rather swing?
Golf club or grand father clock pendulum?

16. Friction Affects the motion of an object A force that opposes motion
Friction reduces the speed of an object and releases heat.
The amount of friction depends on:
Texture of the surface
Weight of the object being pushed or pulled
The amount of force.

17. Gravity Affects the motion of an object Force of attraction
The earth is so large that ALL objects are attracted to it
Gravity depends on
Mass
Distance

18. Balanced VS Unbalanced forces
net force = 0
No motion
Total amount of force on an object
Unbalanced forces –
net force is greater than (>) 0
Motion
Object acted on shows movement in one direction.

19. Are these activities balanced or unbalanced forces?

20. FORCE
A push or pull
Result in motion

21. Mass The amount of matter in an object. NOT Weight of an object
Your mass is the same whether on Mars, Earth or the Moon. Your weight will change.
Ping Pong Ball vs. Marble
Feather vs. cotton ball
Stick vs bamboo

22. Motion
A change in the position of an object with respect to time.

23. Simple Machines
Lever
Inclined Plane
Wheel and Axle
Wedge
Pulley
Screw

24. Work
The application of a force to an object to move it a certain distance in the direction of the force.
Work = force X distance
W = F X D
Work is measured in joules (j)

25. Work you do on a machine is input work
Input Vs. Output
Work you do on a machine is input work
You apply a force to the machine and move it through a distance
Work done by the machine is work output.

26. How do Simple Machines make Work Easier?
It is a device that makes work easier by changing the size or direction of a force.

27. Inclined Plane Definition How is work made easier Examples (3)
A straight, slanted surface
It is easier to push an object up a ramp than it is to lift the object straight up.
Loading a moving truck, slide, wheel chair ramp

28. Wedge Definition How is work made easier Examples (3)
An inclined plane that is wider or thicker at one end than the other.
When moved a wedge is used to cut, split, or pry apart objects
Door wedge to hold open a door, scissors, axe, knife blade

29. Screw Definition How is work made easier Examples (3)
An inclined plane that is wrapped around a cylinder
Force is applied over a long distance. Longer the threads the more work.
Screw, Spiral staircase, top on a bottle

30. lever Definition How is work made easier Examples (3)
Made up of a bar that pivots at a fixed point called a fulcrum
Based on location of fulcrum and load the work is easier. They apply force to a load.
hammer, see-saw, wheelbarrow,

31. Pulley Definition How is work made easier Examples (3)
Rope or chain wrapped around a wheel
Changes the direction of the effort force and/or multiplying effort.
Crane, bike, flag pole and flag, climbing gear

32. Wheel and Axle Definition How is work made easier Examples (3)
Consists of two circular objects of different sizes.
Gets more force from the effort compared to the distance.
Wheelbarrow, doorknob, bike wheel