1. Chapter 2: The Nature of Forces
Newton’s Laws
2-1 Force
A force is a ___________ or a ________________.
A force gives ____________ to an object, sometimes causing it to
_______ _______, stop ______________, or change _________.
Forces work in ____________.
When motion occurs it is due to an _____________________ force.
unbalanced
Forces do not ALWAYS produce ____________________________.
*
When two forces that are equal meet “head on” they are considered ___________________.
Vectors are arrows used by physicists to show the __________ and ______________ of a force.
The head of the arrow shows the _________________ of the force.
The tail (or length) of the arrow shows the ____________________ of the force.
* change in

2. How to determine if an object
is experiencing balanced or
Unbalanced forces...
1. Is it speeding up? Yes /no
2. Is it slowing down? Yes / no
3. Is it changing direction? Yes/no
If you answered
yes to any
of these... it is experiencing
Unbalanced forces.
If all were
balanced.
NO , then the forces are

3. 2-2
Friction
force
Friction is a _____________ that causes motion to _______ down and then ____________.
There are different types of friction. One is ______________ friction that occurs between two irregularly shaped surfaces, another is ____________
friction which usually involved a round object and finally ____________ friction which involves either liquids or gases.
rolling
fluid
weight
You can increase friction by increasing ____________________ or by changing the _________________ of one or both objects.
surface
sliding
rolling
You can decrease friction by changing from _____________ friction to ________________ friction by adding a rounded object or by adding a
__________________ which changes the friction to fluid friction.
gas or liquid
bad
good
Friction is neither __________ nor _____________. It has many positive uses but can also cause problems.
An example of sliding friction occurs when you rub your hands together to warm them.
An example of rolling friction is the tires on your car touching the road.
An example of fluid friction is when the wind blows through your hair and messes it up.

4. 1. Rub your hands together. What do you observe?
2. If your hands were wet, what would be different? Come up
with as many differences as you can.
3. What would happen if your hands were made out of
sandpaper?

5. 2-3
Newton’s Laws of Motion
**Newton’s Laws explain every situation where there is motion, and also the situations where there is none.**
There are ________ laws.
Law #1 states that an object stays in motion or stays still until acted upon by an ________________ _________________.
_______________ is the tendency of matter to stay in place or continue moving. It comes from how much mass something has.
Law #2 states that ________________ and _________ are related.
The equation is: F = MA (Force=mass x acceleration)
The unit Isaac Newton named as his unit of force is a ______________________.
The kilogram is what physicists use as the ___________________.
The m/s/s is the unit used to describe ______________________.
Newton’s 3rd Law states that forces come in _____________ . It also states that when a force acts on something, there will be a
_____________________ that is equal to the force.
Let's do some practice problems using Newton's 2nd Law below (or on your lined paper).
1. John exerted 2N of force on a 1 kg. object. What is the objects acceleration?
Begin with the Verbal Model.
Force = mass x acceleration
Next, fill in what the word problem gives you.
2N = 1 kg. x acceleration
Now, you may want to substitute in a variable to represent the acceleration (a).
2N = 1 kg. x a
With simple numbers like these you may just solve it, or you can "isolate the variable".
2N/1 kg.= 1 kg. x a/1 kg.
Then simplify
2N/1 kg. = a
Do the appropriate math (divide) and properly label.
2 m/s/s = a
So, what this problem says is: "When two Newtons of force are applied to a 1 kilogram mass, the 1 kilogram mass will accelerate at 2 m/s/s.
Now solve this problem.
2. Gabriella, whose mass is 22 kg. was running at 5 m/s/s. She was not looking where she was going and ran into Lucas. How much force
hit Lucas?
3. Lucas has a mass of 33 kg. When Gabriella ran into him, how much did he accelerate backwards as a result of the collision?