1. Forces & Motion Review

2. What is Energy?
Kinetic Energy– objects in motion based on mass and speed Potential Energy—objects have stored energy because of position based on weight and height from the ground

3. Describe Motion

4. Motion When an object changes its position, motion has occurred.
Distance- How far an object has moved.
Displacement- How far an object has moved in relation to its starting point.
Example: Two runners travel along the same straight path in a straight line for 500 meters. At the end of the run their distances are the same but their displacements are different. How can this be so?

5. Displacement vs. distance
a. Distance – how far
something moves(entire Pathway)
b. Displacement – the
distance and direction
of an object’s change in
position from its starting point

6. The hydrant– the hydrant is what the dog’s motion is being judged by.
Review Question
A dog is running past a fire hydrant, relative the hydrant the dog is traveling at 5m/s. What is the reference point?
The hydrant– the hydrant is what the dog’s motion is being judged by.
If a butterfly moves from one flower to another that is 5 meters away, but returns to the original flower?
What is the distance the butterfly traveled?
What is the displacement of the butterfly?
10m 0m

7. Describe Speed

8. Describe Speed A way to describe motion
Average speed - Rate of motion calculated by dividing the distance traveled by the amount of time it takes to travel that distance
Constant speed - Speed that does not change
Instantaneous speed - Speed of an object at any given time

9. What is the formula used to calculate speed?

10. What is the formula for calculating speed?
Speed is calculated by dividing distance by time –

11. Calculate This Speed
A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast was the football player running?

12. Remember to include the UNITS!!
Calculate this Speed:
A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast was the football player running?
Speed = Distance ÷ Time
Speed = 100 m ÷ 20 s
Speed = 5m/s
Remember to include the UNITS!!

13. Distinguish Between Speed & Velocity

14. Distinguish Between Speed and Velocity
Speed describes distance and time
Velocity describes distance, time, and direction
Velocity uses displacement instead of distance when calculating Average Velocity

15. Review Question
A ball is kicked west 150 meters in 15 seconds.
What is the balls velocity?
V= d/t V= 150/15 V= 10m/s west
If a boy is walking west at 3m/s on a train going east at 60m/s? What is the boys resultant velocity?
V= 60m/s E – 3m/sW
V= 57m/s East

16. Interpret The Graph Below:

17. Interpret The Graph Below:
The graph shows an object which is not moving (at rest).
The distance stays the same as time goes by because it is not moving.

18. Interpret The Graph Below:

19. Interpret The Graph Below:
The graph shows that the objects distance increases as time passes. The object is moving and so it has velocity.
The straight line shows it is a constant (not changing).

20. Interpret The Graph Below:

21. Interpret The Graph Below:
Just like the previous graph, this graph shows an object moving with constant velocity

22. Interpret The Graph Below:

23. Interpret The Graph Below:
The curve in the graph shows that the objects velocity is changing as time passes.
This is acceleration.

24. Interpret The Graph Below:

25. Interpret The Graph Below:
In the first part of the graph the object is moving with constant velocity.
In the second part of the graph the object is at rest (not moving).
In the third part the object is again moving with constant velocity.

26. Analyze the Graph Instantaneous Speed .2km/min 6km 6km
What does each dot on the graph
Represent?
What are the changes in Motion?
What is the average Speed of this
Object?
What is the Distance Traveled?
What is the Displacement?
Instantaneous Speed
Constant speed then
an increase in speed at aConstant rate, then stopped
then a constant speed again
.2km/min
6km
6km

27. Describe Acceleration

28. Describe Acceleration
A change in velocity – which may be:
A change in speed
Starting
Stopping
Speeding up
Slowing down
A change in direction
Acceleration is caused by unbalanced forces
More

29. Describe Acceleration
Deceleration is also called negative acceleration - it means an object is slowing down
When acceleration is calculated, it may be a negative number

30. Review Question
A child is riding in a circle at a constant speed. Is the child accelerating?
Yes, because of a change in direction.
Is a car slowing to a stop, acceleration?
Yes, because a change in speed is acceleration
A baseball is traveling across the field at 30m/s and then slows to a speed of 10m/s in 5seconds. What is the balls acceleration?
Vf- Vs = m/s – 30m/s = --20m/s= --4m/s/s
t s s

31. Interpret The Graph Below:

32. Interpret The Graph Below:
The graph shows that the objects velocity does not change as time passes.
It shows constant velocity.

33. Interpret The Graph Below:

34. Interpret The Graph Below:
The graph shows that the objects velocity is increasing as time passes – it is accelerating.
The straight line shows that it is constant acceleration.

35. Which line had a constant speed or no acceleration?
Which Line shows deceleration?
Which line shows faster acceleration B or D? C A
B --steeper Slope
than D

36. Explain Forces

37. Explain Forces
When all the forces acting on an object equal each other : they are balanced
Balanced forces do not cause a change in motion
When one force is greater than another it forms unbalanced forces.
Unbalanced forces equal movement in the direction of the greatest force

38. How Can Forces Affect Objects?
Slow them down
Speed them up
Stop them
Start them
Change their direction
Change their shape

39. Types of Forces Gravity: pulling force exerted on all objects
Friction: pushing force that opposes motion
Caused by the contact of small ridges and valleys between objects

40. Review Question
A mouse pulls with a force of 10 N on a piece of cheese that weighs 5N. What is the net force? Is there movement?
Yes, because the net force is 5N in the direction the mouse pulled.
A furniture mover exerts 100N of force on a piano that weighs 100N. What is the net force? Is there movement?
NO, because the net force = zero. No movement. The furniture mover’s force must exceed 100N.
3. Is sitting in a chair an example of balanced or unbalanced forces?
Balanced

41. Describe Friction

42. Describe Friction
Force that resists motion between two touching surfaces
Acts in the opposite direction of the object’s motion
Produces heat

43. Describe Friction
2 Types: Kinetic: occurs when moving objects are in contact
Static: occurs when objects are in contact but not moving
Sliding Friction takes more force to oppose than Rolling Friction

44. Describe Friction
Helpful : friction helps us walk, brake and stop and hold things without dropping them Harmful: friction can wear out parts on a machine, wear holes in socks, and prevent you from sliding down a slide Increase friction by: increasing force pressing objects in contact or increase the roughness of the surface of the objects in contact Decrease friction by: smoothing the surface Using lubricants: water, oil, wax etc

45. Indicate if the friction is helpful or harmful Soil erosion---
Review Question
Indicate if the friction is helpful or harmful
Soil erosion---
Car tires’ tread wearing down
Brakes stopping your bike
Walking without slipping
Rubbing your hands to warm them
a hole developing in your sock
Increasing Friction or Decreasing Friction
Using a cooking spray in the pan before cooking eggs
Pushing harder on the eraser to remove stray marks on a wall
Using a tissue with lotion on a runny nose
Wearing batting gloves
Waxing skies before using them
harmful
harmful
Helpful
Helpful
Helpful
harmful
decrease
Increase
decrease
Increase
decrease