12.1 Forces
A ____________________________ is a push or a pull
We experience many types of forces each day: _____________________________________________
Forces can cause objects at rest to ___________________, or it can cause objects in motion to accelerate by
changing the object’s ______________________________ or __________________________
Some forces are ___________________________ forces, but others do not require objects to be in contact
Forces are measured in units called ______________________________________
One Newton of force causes an object with a mass of 1 kg to accelerate at 1 m/s2, so 1 N = _______________
You can use _________________________ to represent forces; a longer arrow indicates a greater force
Combining Forces
There can be _______________ forces acting on an object at one time.
Force arrows can be used to show the result of how forces combine
Example: Pushing a car
The _________________________ is the overall force acting on an object after all the forces are combined
Forces in the same direction are _________________ and forces in opposite directions are ________________
When the forces are balanced, the net force equals __________ and there is no change in the object’s motion
*** This does NOT mean the object stops moving-could mean continues moving with a constant velocity***
If the forces are not equal they are unbalanced, and it causes an object to ______________________
TUG-OF-WAR EXAMPLES:
100 N
100 N

The forces shown above
are PUSHING/PULLING forces
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The forces shown above
are WORKING TOGETHER/
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OPPOSITE FORCES
The forces are EQUAL/ NOT EQUAL
The forces DO/ DO NOT balance each other
The resultant force is 100 N TO THE RIGHT/ 100 N TO THE LEFT/ ZERO
There IS/ IS NO motion

The forces shown above are PUSHING/PULLING forces

The forces shown above are WORKING TOGETHER/ OPPOSITE FORCES

The forces are EQUAL/ NOT EQUAL
The forces DO/ DO NOT balance each other
The stronger force is pulling to the LEFT/ RIGHT
The resultant force is 300 N TO THE LEFT/ 300 N TO THE RIGHT/ ZERO
The motion is to the LEFT/RIGHT
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Friction
Friction is the force that _______________________ of objects as they move past each other (a contact force)
There are ______________ main types of friction:
1) Static friction-acts on objects that are _________________________ (keeps them from moving)
2) Sliding friction-opposes motion of objects as they _______________ across a surface (static > sliding)
3) Rolling friction-Acts on objects ____________ across a surface (100-1000 times less than static or sliding)
4) Fluid friction- opposes motion of an object through a ______________ (this force increases with velocity)
Gravity
Gravity is the force that acts between two masses and is an attractive force (not a contact force)
Gravity acts toward the _________________________
Free Fall
Freely Falling objects are accelerated downward by _________________ and upward by _________________
Eventually those two forces will balance and the object reaches _________________________
Projectile Motion is the curved path of an object falling when it has an initial forward velocity
VIDEO DEMO: Which hits the ground first: a 5kg weight that is dropped or a 5 kg weight that is thrown
horizontally?
12.1 Questions
1. How is the motion of an object affected when a force acts on it?
2. What is the unit of force and what does it equal?
3. How can an arrow be used to represent the size and direction of a force?
4. The overall force acting on an object after all the forces are combined is the ______________________.
5. If all the forces acting on an object are balanced forces, what does the net force equal?
6. How do balanced and unbalanced forces affect the motion of an object?
7. List the four types of friction:
8. What type of friction acts on objects at rest?
9. How does air resistance affect the acceleration of a falling object?
10. Explain how skydivers eventually reach a terminal velocity:
11. Define gravity:
12. Earth’s gravitational force acts in what direction?
13. Rank the strengths of static, sliding, and rolling friction from strongest to weakest:
STRONGEST-------------------------------------------------------->WEAKEST
14. Explain why falling leaves often do not fall in a straight line path to the ground:
15. Two coins are knocked off a table at the same time by different forces. Which coin will hit the floor first?
Chapter 12.2: Newton’s 3 Laws of Motion
Newton’s 1st Law: AKA The Law of Inertia
Newton’s 1st Law states that an object at rest ________________________ while an object in motion
___________________________ unless an ___________________________ force acts on it.
Examples of Newton’s 1st Law:
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Inertia and gravity are what keep objects in ________________ around other more massive objects
The amount of inertia an object has depends on the object’s _________________
Newton’s 2nd Law: AKA F=ma
Newton’s 2nd Law states that _________________________________________________________
Examples of Newton’s 1st Law:
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This means that a larger force acting on an object will create a ___________________ acceleration
It also means that a larger mass will cause a _____________ acceleration if the force is constant
(Because lighter objects are easier to accelerate, and heavy objects are harder to accelerate)
The formula for Newton’s 2nd Law is:
Newton’s Third Law: AKA Action-Reaction Law
Newton’s Third Law states that _______________________________________________________
Give examples of Action Reaction Forces:
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Do all action-reaction pairs produce motion?
Why don’t all action-reaction force pairs cancel each other out?
Mass vs. Weight
What is the difference between mass and weight?
How will your mass and weight differ on the Earth and the Moon?
Chapter 12.2 Questions
1. State Newton’s Three Laws of Motion in your own words:
1st Law: ________________________________________________________
2nd Law: ________________________________________________________
3rd Law: ________________________________________________________
2. Which Law is also called the Law of Inertia? __________________________________
3. What equation states Newton’s Second Law of Motion? _________________________
4. If you increase the force on an object what happens to the acceleration?
5. If you use the same force on a less massive object what happens to the acceleration?
6. How is mass different from weight?
7. The Moon’s gravity is only one sixth that of Earth’s Explain how the mass and weight of an object
differ between the two locations.
8. Which Law of Motion explains the relationship among force, mass, and acceleration?
9. Which law is known as the law of action-reaction?
10. Which law explains why you fall backwards when you bump into something?
11. If you double the force of an object what happens to the acceleration?
12. If you double the mass of an object what happens to the acceleration?
13. When Jane drives to work, she always places her purse on the passenger’s seat. By the time she
gets to work, her purse has fallen on the floor in front of the passenger seat. One day, she asks
you to explain why this happens in terms of physics. What do you say?
14. You are waiting in line to use the diving board at your local pool. While watching people dive into
the pool from the board, you realize that using a diving board to spring into the air before a dive is a
good example of Newton’s third law of motion. Explain how a diving board illustrates Newton’s third
law of motion.
15. You know the mass of an object and the force applied to the object to make it move. Which of
Newton’s laws of motion will help you calculate the acceleration of the object?
PRACTICE PROBLEMS:
1. A boy pushes forward a cart of groceries with a total mass of 40.0 kg. What is the acceleration of
the cart if the net force on the cart is 60.0 N?
2. What is the upward acceleration of a helicopter with a mass of 5000 kg if a force of 10,000 N acts
on it in an upward direction?
3. An automobile with a mass of 1200 kg accelerates at a rate of 3.0 m/s2 in the forward direction.
What is the net force acting on the automobile?
4. A 25-N force accelerates a grocery cart at 0.5 m/s2. What is the mass of the cart?
5. Your shopping cart has a mass of 65 kilograms. In order to accelerate the shopping cart down an
aisle at 0.3 m/sec2, what force would you need to use or apply to the cart?
6. A small child has a wagon with a mass of 10 kilograms. The child pulls on the wagon with a force of
2 newtons. What is the acceleration of the wagon?
7. You dribble a basketball while walking on a basketball court. List and describe at least 2 pairs of
action-reaction forces in this situation.
8. What is the acceleration of a 6.4 kilogram bowling ball if a force of 12 N is applied to it?
9. CHALLENGE: What is the mass of an object that needs a force of 6 600 N to increase its speed
from rest to 107 m/s in 2.3 seconds? (HINT: FIND “a” first)
Chapter 12 Lessons 1 and 2 Review:
Name: ______________________ Hour: ______
1. A ___________________ is a push or a pull
2. The SI unit of force is the ______________________.
3. If the forces acting on an object produce a net force of zero, the forces are called _________________.
4. Forces that are equal in size but opposite in direction are called ____________________ forces.
5. ____________________ forces acting on an object cause the object to accelerate.
6. Newton's first law states that an object remains at rest unless a(n) ________________ force acts on it.
7. Forces that are equal in size but opposite in direction are ____________________.
8. If a net force acts on an object, the object accelerates by changing _____________ or _____________.
9. When a pair of balanced forces acts on an object, the net force that results is equal to _____________.
10. Friction is a force that ____________________motion between two surfaces that are in contact
11. While pushing a box up a hill, you have to overcome ____________________ friction.
12. If a heavy box does not move when you push it, it is because the ______________ friction is too great.
13. What kind of friction occurs as a fish swims through water? ____________________.
14. When a ball is dropped, it falls down due to the force of ____________________.
15. The force of gravity exists between any two objects that have _____________
16. The two forces acting on a freely falling object are gravity and ____________________.
17. When a falling object reaches terminal velocity, the net force acting on it is ____________________.
18. Air resistance____________________as you move faster.
19. The force of gravity causes all objects near Earth's surface to fall with an acceleration of ___________.
20. The tendency of an object to resist any change in its motion is called ____________________.
21. Inertia varies depending on____________________.
22. The curved path of an object with an initial forward velocity is an example of ______________ motion.
23. Projectile motion is caused by an initial ____________________ velocity
24. The sum of all the forces acting on an object is called the ____________________.
25. Which Law of Motion explains or states the following?
_________________
Jim improved his lap time by purchasing a lighter bicycle
_________________
Jim can throw farther than me because he can apply more force
_________________
For every action there is an equal and opposite reaction
_________________
An object will move at a constant speed unless a force acts on it
_________________
A rocket takes off when the thrust of the engines pushes down
_________________
A fireman’s water hose pushes him back in the opposite direction
_________________
Jill crashed her bike into the fence and was thrown over it
_________________
Acceleration of an object is directly proportional to the force on it and
_________________
Associated with the formula: F=ma
Problems:
26. What is the rate of acceleration of a 2,000-kilogram truck if a force of 4,200 N is used to make it start
moving forward?
27. What is the acceleration of a 0.30 kilogram ball that is hit with a force of 25 N?
28. How much force is needed to accelerate a 68 kilogram-skier at a rate of 1.2 m/sec2?
29. What is the mass of an object that requires a force of 30 N to accelerate at a rate of 5 m/sec2?
30. What is the force on a 1 000 kilogram-elevator that is falling freely under the acceleration of gravity only
(9.8m/s2)?
31. What is the mass of an object that needs a force of 4 500 N to accelerate it at a rate of 5 m/sec2?
FORCE Bingo Review Questions:
Name: ________________ Hour: ______
_______________ 1. Who created the 3 Laws of Motion? (USE AS YOUR FREE SPACE)
_______________ 2. Which law is responsible for launching a rocket into space?
_______________ 3. What is the sum of all forces acting on an object?
_______________ 4. What characteristic of a force vector arrow shows the strength of the force?
_______________ 5. What law states that an object in motion stays in motion until a force is applied?
_______________ 6. What is the total amount of matter of an object?
_______________ 7. What does the net force have to equal in order for the object to not move?
_______________ 8. What is the unit for force?
_______________ 9. What is the attractive force that exists between any 2 objects with mass?
_______________ 10. What will happen to the force of gravity if distance increases?
_______________ 11. Which direction will an object move if forces of 100 N right and 120 N Left act on it?
_______________ 12. What law states the relationship between mass, force, and acceleration?
_______________ 13. What is a push or a pull?
_______________ 14. What is the formula for Newton’s 2nd Law?
_______________ 15. If you increase the mass of an object, what happens to acceleration if force is constant?
_______________ 16. Which law states that a football on the tee will just stay there until someone kicks it?
_______________ 17. Which Law can be stated as F=ma
_______________ 18. What does the pointy end on a Force vector arrow show you?
_______________ 19. What is an increase or decrease in speed or a change in direction?
_______________ 20. What is the tendency of an object to resist changes in motion?
_______________ 21. What will happen to the force of gravity if mass increases?
_______________ 22. What is the measure of the force of gravity acting on an object?
_______________ 23. Which law states that for every action, there is an equal and opposite reaction?
_______________ 24. What type of force causes a change in motion?
_______________ 25. What type of friction slows down the acceleration of a falling object?
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Lesson 12.3: Newton’s Third Law of Motion and Momentum
Newton’s Third Law
A force cannot exist alone- they always exist in pairs called ___________________________________
Examples of Action Reaction Forces:
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Not all action-reaction force pairs produce motion: ________________________________________
Why don’t all action-reaction force pairs cancel each other out? _____________________________________
For example: _________________________________________________________________________
If the action-reaction forces act on same object, they do cancel each other out and net force = _____________
Momentum
Momentum is the product of _________________________________________
An object with a large momentum is difficult to __________________________
Think-Pair-Share Question: Which is easier to stop: a bowling ball or a marble?
Any object at rest has a momentum equal to _________________because ____________________________
A huge rocket on a launch pad has zero momentum but a tiny meteor traveling fast has a ton of momentum
Conservation of Momentum
During collisions, the total momentum of the system is ________________________________
The total momentum of the system before the collision ___________ the total momentum of the system after
This is only true in a closed environment and does not happen this way in the real world because of _________
Momentum is _____________________ during collisions
If one object loses momentum, the other one ________________________
12.3 Questions
1. Using Newton’s third law, explain what is meant by action and reaction pairs of forces:
2. State in your own words the formula for momentum:
3. What is a necessary condition for the conservation of momentum?
4. If an eagle and a bumblebee are traveling at 8 km/hr, which has more momentum?
5. A friend tells you that a rowboat is propelled forward by the force of the oars against the water:
a) Explain whether the statement is correct:
b) Identify the action and reaction forces involved:
6. Explain how Newton’s Third Law of Motion is at work when you walk:
7. Explain in terms of Newton’s third law why someone who tries to jump from a canoe to a riverbank may fall
into the water.
8. What must you know about two vehicles travelling at the same velocity to determine which has more
momentum?
9. Calculate the momentum of a 80-kg runner moving at a speed of 2.5 m/s:
10. If the momentum of an object is 1000 kg m/s and the velocity of the object is 2 m/s, what is the mass of
the object?
Lesson 12.4: The Universal Forces
Scientists’ observations strongly suggest that there are __________ universal forces
The universal forces are:
1) _________________________________
2) _________________________________
3) _________________________________
4) _________________________________
The four universal forces act over distances which means ______________________________
Electro-magnetic force:
(EM was considered to be 2 different forces, but they are just different aspects of the same force)
There are two aspects of this force: _________________ and ________________ forces
These are the only types of forces that can both __________________ and _________________
Electric forces act between charged particles such as ________________ and _____________
Objects with opposite charges _______________ and like charges ___________________
Magnetic forces act on some metals, the polar ends of magnets, and ___________________________
Strong Nuclear Force:
The strong nuclear force is a powerful force of attraction that acts only on __________________
Although it acts only over short distances, it is 100 times stronger than the _________________
Weak Nuclear Force:
The other powerful force in the nucleus but is weaker and acts over a _____________________
This is the force responsible for radioactive ________________
Gravitational Force:
Gravity is the _______________________ universal force
It was ______________________ who discovered that gravity affects all objects in the universe
Gravitational force is an attractive force that acts between any two objects with ________________________
Newton’s Law of Universal Gravitation states that _________________________________________________
How do mass and distance affect the gravitational force? ___________________________________________
Although gravity is the weakest universal force, it acts over _________________________________________
Gravity is responsible for keeping things in orbit such as ____________________________________________
Newton’s Third Law and Law of Universal Gravitation are related:
The gravitational force between the Earth and the Moon goes both ways. The moon’s gravitational force
causes what phenomenon on Earth?
Satellites in Orbit
Satellites in low orbits experience ________________ due to the Earth’s atmosphere
When satellites lose speed, their altitude _________________ and eventually they burn up in the atmosphere
12.4 Questions
1. What are the 4 universal forces?
2. T or F: The electromagnetic force is associated with charged particles.
3. Which universal force can attract as well as repel?
4. Which universal force acts to hold the nucleus together?
5. State in your own words what is meant by Newton’s Law of Universal Gravitation:
6. How does friction with the atmosphere affect the speed of artificial satellites?
7. The moon in its orbit around the Earth behaves like a ball at the end of a sting being swung above your
head. Explain the forces involved.
8. If the speed of an orbiting satellite decreases, how might you expect its orbit to change?
9. Explain how Newton’s Third Law and the Law of Universal Gravitation are connected:
10. Gravitational force between two objects depends on _______________ and ____________________
11. The farther apart two objects are, the ___________________ the gravitational force.
12. The greater the mass of an object, the ___________________ its gravitational force.
Chapter 12 Review:
NOTE: Studying only these 12 questions is not enough!!! Don’t forget to also look over:
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the study guide for quiz #1

your notes for 12.3 and 12.4 (especially the questions at the end of each section)

the online quizlet (http://quizlet.com/35543692/chapter-12-force-flash-cards/)

the flashcards posted on Teacher Web
This page is meant for extra practice ONLY, and these are not the only topics to know for your test!!!
1. When shooting an arrow at a target, why is it advisable to aim above the bull’s-eye rather than at it?
2. When a tennis player hits a ball against a wall, which of Newton’s Laws of Motion is he making use of?
3. The moon’s gravity is 1/6 the Earth’s. How will weight and mass differ between the two locations?
4. During a fuel economy test of a car, it was determined that the car got better gas mileage with the
convertible top up. Explain why this might be true:
5. How can changes in mass and force increase the acceleration of an object?
6. Hovercraft can achieve greater speeds than ordinary boats. Explain why this is possible.
7. Which object has a greater momentum:
a. A huge boulder at rest
c. a small pebble tossed into the air
b. A baseball after struck by a bat
d. a car speeding down the highway
8. A 100-kg crate, sliding on a floor, is brought to a stop by a 25-N force. What is the deceleration of the
crate?
9. What is the momentum of an 80-kg runner moving at the speed of 2.5 m/s?
10. What is the force acting on a 1200-kg car if the car is accelerating at 3.0 m/s2?
11. What is the mass of a bowling ball with a momentum of 42 kg m/s traveling at a velocity of 6.0 m/s?
12. What is the acceleration of a 2500-kg truck acted on by a 250-N force?