1. force              6. work                  11. potential energy
                                             2. mass              7. newton              12. power
                                             3. weight            8. energy               13. acceleration
                                             4. inertia             9. joule                  14. deceleration
                                             5. speed           10. kinetic energy     15. friction

FORCE - a push or pull
- it always takes a force to put an object into motion
- forces are either balanced or unbalanced
- balanced means the forces are equal and opposite to each other
- unbalanced means one force must be greater than the force that opposes motion

MOTION - occurs when the opposing forces are unbalanced

FRICTION - a force that opposes motion
- examples: 1) tires against the road    2) air resistance

MASS - the amount of matter in an object
- mass is constant, it remains the same regardless of gravity
- NOTE: mass is measured in grams or kilograms using a balance

WEIGHT - is a measure of the force of gravity on an object
- the weight of an object can change depending on the gravity acting on it.
- NOTE: weight is measured in newtons (pounds in the English System) using a spring scale

NEWTON (N) - the metric system unit of force
 
 
 
 
 
 
 
 
 
 
 
 

Mass and Weight are not the same:
- mass measures the amount of matter in an object
- weight measures the gravitational force acting on an object

EXAMPLE: A person's weight changes if the gravity is changed.

            980 newtons     245 newtons    109 newtons
EARTH 100 kilograms   100 kilograms   100 kilograms
In the example, the person's weight changes due to less gravitational pull from the earth, but his mass remains the same.

NOTE: A person's mass would remain constant anywhere in the universe.

PROBLEM: The moon's gravity is 1/6 of the earth's. What would your weight be on the moon?

Example: A person who weighs 480 newtons (120 pounds) on the earth would weigh 1/6 (480 newtons) or 80 newtons (20 pounds) on the moon.

GRAVITY - a mutual force of attraction which exists between all objects in the universe.
- NOTE: every object (small or large) pulls (has gravity) on every other object.

- The more mass an object has the greater its gravitational force.
- As the distance between two objects increases the attraction (gravity) between them decreases.
 
 

- an object at rest tends to remain at rest
- an object in motion tends to remain in motion at the same speed and in the same direction.
- INERTIA - refers to the tendency of an object to resist changes in motion.
- NOTE: It takes a force to start and stop motion.

- EXAMPLE:
a) the faster a car moves, the greater the resistance to change the motion; therefore, the greater the distance required for stopping.
b) A car gets better gas mileage on the highway than in city driving. How does this relate to Newton's First Law? Hint: It is harder (takes more force) to start something moving (to overcome the inertia of rest) than it does to keep it moving.
c) Explain how seat belts and air bags used in some vehicles relate to the first law of motion.
 
 

The acceleration of an object is:
1. directly proportional to the force applied to the object. More force = more acceleration - EXAMPLE: If you swing a bat harder (with greater force) the ball will accelerate off the bat faster.
2. inversely proportional to the mass of the object. The more mass the object you are trying to accelerate has, the more force will be necessary to accelerate it. - EXAMPLE: If you would swing and hit a bowling ball with the bat instead of the baseball, the bowling ball would obviously accelerate off the bat much more slowly.
Acceleration - the rate of increase in speed.

EXAMPLES OF THE SECOND LAW:
1. By pressing down on a car's gas pedal, more gas is sent to the engine, thereby creating more force, which results in an increase in acceleration.
2. It takes more force to stop a freight truck than a car (due to the truck's greater mass).
3. A larger force is required to move a bookcase filled with books than an empty bookcase.
 
 

- when one object exerts a force on another, the second object will exert an equal force in the opposite direction (action-reaction).

EXAMPLES: a rocket blasting off

a. air escaping from a balloon
 
 

action reaction
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

WORK - the product of the force applied to an object and the distance the object moves.

work = force x distance
w(joules) = f(newtons) x d(meters)

NOTE: the unit of work is the joule

1 joule = the amount of energy or work required to maintain a force of one newton through a distance of 1 meter.

Example: A force of 100 newtons is applied in lifting a block 2 meters.

Find work.
 
 
 

SOLVE THE FOLLOWING PROBLEMS:

1. Find work, if it takes 500 newtons of force to move a box 5 meters.

2. Find the distance a box is moved if work is 200 joules and the force is 100N.

3. Find the force necessary to slike a box 5mm if the work required to do the job is 500 joules.
 
 
 
 
 
 
 
 
 
 
 
 
 
 

POWER - the amount of work done per unit of time.

Power (watts) = work (joules)/ time (seconds)

Example: Find power if it takes 10 seconds to do 200 joules of work.

Solution: p = w/t  therefore,  power = 200J/10s = 20 watts
 
 
 
 
 
 
 
 
 
 
 
 
 
 

ENERGY - can be considered the ability to do work.
 

TYPES OF ENERGY:
1. Kinetic energy - energy of motion
- Examples: - a moving car has energy of motion
- the blades of a rotating fan
- a rolling ball
- NOTE: the amount of kinetic energy a moving object has depends on the mass of the object and its velocity.

2. Potential energy - energy of position.
- Examples - fuel is an example of both types of energy
- unused it has potential energy (capable of doing work)
- when burned the fuel becomes kinetic energy
- Other Examples: a wound spring, an unexploded bomb, firewood, food)
- NOTE: One form of energy can be converted to another form.
 

FORMS OF ENERGY - mechanical, heat, chemical, electrical, nuclear, light, magnetism, sound.