1. Motion and Force
Chapters 5 and 6

2. Frame of Reference
You compare something not moving with some thing moving.
The stationary object is called a frame of reference.

3. Reference objects depend on the type of movement and your position
Reference objects depend on the type of movement and your position. The most common frame of reference is the Earth.
Frame of Reference

4. Motion Distance Definition:
The change in position in a certain amount of time; always comparing with a frame of reference.
Motion
Distance
The length between two places. It is measured on meters (m) and kilometers (km).
Distance = Time x Speed; D=T x S.
Time is measured in seconds or hours.

5. Speed The rate at which an object moves.
Speed = Distance divided by time
S = d/t.
The unit used to measure speed is meters per second (m/sec) or kilometers per hour (km/hr).

6. Constant Speed Speed does not change.
Use a distance/time graph to display your information.
Constant speed is a straight line.

7. Velocity The speed of an object in a particular direction
Do not get confused with speed, not the same thing
Must have a direction (N, S, E, W)
Velocity

8. Velocity and Acceleration
The rate of change in velocity is known as acceleration.
If an object is accelerated it is speeding up, slowing down, or changing direction.
Average Acceleration = final velocity minus original velocity divided by time
Velocity and Acceleration

9. Circular Motion
In circular motion, the velocity is continuously changing because the direction is continuously changing.
An object in circular motion is accelerating even though its speed may be constant.
Centripetal acceleration is acceleration that occurs in a circular motion

10. What is Force?

11. Force is….. A push or a pull. All forces have both size and direction.
Forces are everywhere!
When something is moving, a force created the movement!
Force equals mass (kg) times acceleration (9.8 m/s2)
F = m x a
Forces are expressed in Newtons (N). The more N, the more force!
Force is…..

12. All forces are exerted by one object on another object.
Just because a force is exerted on an object, does not mean movement will occur.
Forces act on Objects

13. Forces in Combination
When 2 or more forces are exerted on an object at the same time, there is a Net Force.
Net Force: the force that results from combining all the forces exerted on an object.

14. Balanced vs. Unbalanced Forces
Balanced forces do not cause a change in motion. They are equal in size and opposite in direction.
When the net force on an object is not zero, the forces on the object are unbalanced. Ex: Tug of war
Unbalanced forces can also be exerted in the same direction.
Balanced vs. Unbalanced Forces

15. A force that opposes motion between two surfaces that are in direct contact
Can cause a moving object to slow down and eventually stop moving
Two factors that affect the amount of friction include the force pushing the surfaces together and the roughness of the surface
Friction

16. The amount of friction depends on the force pushing the surfaces together
When two surfaces are in contact the hills and valleys of one surface stick to the hills and valleys of the other.

17. Types of Friction Kinetic Friction Friction between moving objects
Sliding friction (brakes on a bicycle)
Rolling friction (anything with wheels)
Types of Friction

18. Types of Friction Static Friction Static means “not moving”
Occurs when a force is applied to an object but the object does not move
The object does not move because the force applied is equal to the static friction
Types of Friction

19. Friction: Helpful and Harmful
Without friction objects would not start to move nor stop moving once motion began
Friction can cause erosion of the topsoil or holes to develop in your clothes
Friction: Helpful and Harmful

20. Friction: Helpful and Harmful
Lubricants are substances used to reduce friction
Oil, grease, wax
Making surfaces smoother also help reduce the amount of friction between two surfaces.
Friction: Helpful and Harmful

21. Friction: Helpful and Harmful
Making surfaces rougher can increase friction
Salt on icy roads, scratching the bottoms of new shoes
Increasing the force applied to a surface can also increase the friction
Pressing harder on wood when sanding it by hand
Friction: Helpful and Harmful