1. Force What is force? 1000 kg Push or Pull
It’s what causes “things” to accelerate
1000 kg

2. Balanced v. Unbalanced Forces
If all forces are balanced there is no acceleration in any direction.
(Either Zero Motion or Constant Velocity)
If one force is greater than the opposing force we get acceleration in a direction.

3. Balanced Forces (Balanced Forces = No Acceleration)
Object
5 N
5 N
Notice that all the forces are equally pointed in the opposite direction. Hence they balance each other – or cancel each other.
Equal Pushing
Forces may cancel each other and produce No Acceleration!

4. Balanced Forces (Balanced Forces = No Acceleration)
Ground pushes up
Gravity pulls down
Gravity pulls down on you…
The ground pushes back up…
THIS KEEPS YOU WHERE YOU ARE!
If these football players push
on each other equally as hard,
will either one move?

5. Balanced Forces (Balanced Forces = No Acceleration)
Equal Pushing
Equal Pulling
5 N
5 N
Forces may cancel each other and produce No Acceleration!

6. Unbalanced Forces Causes Acceleration
Adding Forces
Subtracting Forces

7. Adding Forces
5 N
5 N
= 10 N
Two forces can add together to produce a larger net force than either original force.
Positive Acceleration occurs (Speed up)

8. Unbalanced Forces Causes Acceleration
Adding Forces
Object
5 N
5 N
Notice that all the forces are pointed in the same direction. Hence they add together.

9. Subtracting Forces 10 N = 5 N 5 N
Two forces can subtract to produce a net force in the direction of the larger force.
Negative Acceleration occurs (Slow Down)

10. Unbalanced Forces Causes Acceleration
Subtracting Forces
Object
5 N
5 N
5 N
Notice that all the forces are unequal and pointed in the opposite direction. Hence they are unbalanced and in opposition to each other – or one partially cancels the other.

11. Balanced Forces Balanced Push No Acceleration i.e. Pushing a Car Pull
i.e. Tug-o-war
10N
10N
10N
10N

12. Un-Balanced Forces Un-Balanced Faster Same Direction Acceleration
Additive
Un-Balanced
Same Direction
Faster
Acceleration
Subtractive
Opposite Direction
Slower
10N
10N
10N
10N
10N

13. Balance between Gravity and Friction
Q: If the friction of the air and the pull of gravity were in perfect balance, what
would the skydiver be doing?
A: The skydiver would be going a constant velocity (moving with no acceleration) down towards the ground until it hit the ground.
The skydiver is colliding with the
molecules of gas in the air!
Which slows down the fall of the skydiver!

14. How it works Speed: Air Resistance 0 m/s 25 m/s 28 m/s 20 m/s 10 m/s
Constant Velocity
How it works
Notice that as the skydiver leaves the plane, the force of gravity accelerates him faster towards the earth; however, the moment he jumps out of the plane, another force begins to oppose gravity – Air Resistance, (Friction).
This friction with the air begins to slow down his rate of acceleration. Meaning, he’s still speeding up, just not as fast.
Once the force of air friction equals the force of gravity, the skydiver steadily descends towards earth at a constant velocity.
Accelerating
Accelerating
Air Resistance
30 m/s
0 m/s
Speed:
0 m/s
25 m/s
28 m/s
20 m/s
10 m/s
Constant Velocity
Gravity

15. Balanced Forces (Balanced Forces = No Acceleration)
Wait a minute. This object was moving.
That’s Right. As you may have noticed, although I may have balanced forces, I might still be moving.
Notice that when the forces are balanced, the object might still be moving, but the objects are not accelerating, instead they have a constant velocity. Hence, once in motion – it’s always in motion unless acted upon by what? Another Force.
Object
5 N
5 N
Notice that all the forces are equally pointed in the opposite direction. Hence they balance each other – or cancel each other.
Equal Pushing
Equal Pulling
Forces may cancel each other and produce No Acceleration!

16. Constant Velocity
Distance [m] 1 2 3 4 5
Time [Sec]
In other words, you still need to use the gas peddle to balance out all the force of friction to keep you going at a constant speed.
5 N
5 N

17. To get an object to move faster, create an unbalanced force!
Acceleration 1 2
To get an object to move faster, create an unbalanced force!
10 N
5 N

18. Force 2,667 miles/hr Speed = Distance divided by time S= D/T
What is the speed of a rocket traveling at 4,000 miles in 1.5 hours?
2,667 miles/hr

20. The Law of Conservation of Energy
created
Energy cannot be __________ or ____________; it may be transformed from one form into another, but the total amount of energy _________ changes.
destroyed
never

21. What is energy? “the ability to do work”
The combination of energy and matter make up the universe:
Matter is substance, and energy is the ____________ of substance.
mover

22. Energy is nature’s way of keeping score.
We sense energy only when it changes,
either a transformation from one form of energy to another,
or a transfer of energy from one point to another.

23. How is all energy divided?
Potential
Energy
Kinetic
Energy
Gravitation
Potential
Energy
Elastic
Chemical

24. Potential Kinetic position motion storage energy of _________
or energy in ______________.
Water behind a dam
Hammer over head
Food on the plate
energy of ________, the form capable of doing work
Flowing water
A falling hammer
Food being converted into usable energy in the cell.
storage

25. PE = mgh h m ____ = mass (kg) ____ = height (m)
____ = accel due to gravity
(9.8 m/s2) h g

26. What is Gravitational Potential Energy?
Potential energy due to an object’s position
P.E. = ________x
________ x _____________
mass
height
Don’t look down, Rover!
Good boy!
gravity

27. What is Potential Energy?
Energy that is stored and waiting to be used later

28. What is Elastic Potential Energy?
Potential energy due compression or expansion of an elastic object.
Notice the ball compressing
and expanding

29. What is Chemical Potential Energy?
Potential energy stored within the chemical bonds of an object

30. What is Kinetic Energy? Energy an object has due to its motion
K.E. = .5(mass x speed2)

31. KE = 1/2 m v2 .25 kg baseball 4 kg bowling ball at 50 m/s at 10 m/s
= .5 (.25kg) (50 m/s)2
= 312 J
4 kg bowling ball
at 10 m/s
= .5 (4kg) (10m/s)2
= 200 J

33. Work is done when a force is exerted over a distance.
Courtesy Jerry Ohlinger’s Movie Material Store

34. Work
is equal to the force that is exerted multiplied by the distance over which it is exerted.
W = _______
The unit of work combines the unit of force (N) with the unit of distance (m)
Newton-meter (N-m) aka ________.
F x d
Joule

35. You carry a 20 kg suitcase upstairs, a distance of 4m
You carry a 20 kg suitcase upstairs, a distance of 4m. How much work did you do?
W = F x d
F = ma
= (20 kg) (10m/s2) = 200 N
= (200 N) (4m)
= 800 J

36. 6 fundamental forms of energy
mechanical energy
Thermal (heat) energy
electromagnetic energy
electrical energy
nuclear energy
chemical energy

37. What is the source of our energy?
The source of practically all our energy is the _______.
SUN

38. What is Mechanical Energy?
Energy due to a object’s _________ (kinetic) or __________ (potential).
The bowling ball has mechanical energy.
When the ball strikes the pins, mechanical energy is transferred to the pins!
motion
position

39. Examples of Mechanical Energy

40. What is Electromagnetic Energy?
_________________
Includes energy from gamma rays, xrays, ultraviolet rays, visible light, infrared rays, microwave and radio bands
Light energy

41. What is Electrical Energy?
Energy caused by the movement of _____________
Easily transported through power lines and converted into other forms of energy
electrons

42. What is Chemical Energy?
Energy that is available for release from _____________________.
The chemical bonds in a matchstick store energy that is transformed into thermal energy when the match is struck.
Chemical reactions

43. Examples of Chemical Energy

44. What is Thermal Energy?
Heat energy
The heat energy of an object determines how active its atoms are.
A hot object is one whose atoms and molecules are excited and show rapid movement.
A cooler object's molecules and atoms will show less movement.

45. ELECTROMAGNETIC ENERGY
QUIZ TIME!
What type of energy cooks food in a microwave oven?
ELECTROMAGNETIC ENERGY
What type of energy is the spinning plate inside of a microwave oven?
MECHANICAL ENERGY

46. QUIZ TIME!
Electrical energy is transported to your house through power lines.
When you plug an electric fan to a power outlet, electrical energy is transform into what type of energy?
MECHANICAL ENERGY

47. QUIZ TIME!
What energy transformation occurs when an electric lamp is turned on?
ELECTRICAL ENERGY 
ELECTROMAGNETIC ENERGY

48. What types of energy are shown below?
Mechanical and Thermal Energy
(Don’t forget friction)

49. What type of energy is shown below?
Chemical Energy

50. What types of energy are shown below?
Electrical, Mechanical and
Electromagnetic Energy

51. What type of energy is shown below?
Chemical Energy (yummy)

52. What type of energy is shown below?
Thermal Energy

53. What types of energy are shown below?
Mechanical, Electromagnetic, Electrical, Chemical and Thermal Energy

54. The Law of Conservation of Energy
Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.