1. Unit 2 Forces & Motion

2. Forces ______ occur in pairs!!!!!
______- an _____ applied to an object to _______ its motion(push or pull)
Units of lb, N (equal to kg.m/sec2)
If forces are _______ then the object won’t _______ and it is said to be in __________
_______ _________=acceleration
Forces ______ occur in pairs!!!!!

3. Newton’s Laws of Motion
Newton’s First Law:
“AKA” the Law of _______
Inertia- property of an object to ______ _______ in state of motion
an object will _____ at rest until ______ on by an unbalanced _______
In other words, things tend to keep on doing what they were doing in the first place unless you apply a force.

4. Newton’s Laws of Motion
Newton’s Second Law:
Unbalanced force causes an object to ________ while the object’s mass _____acceleration
Fnet=ma
a=acceleration (m/sec2), F= force (N), m=mass (kg)
Fnet= Right – Left
Fnet= Top - Bottom
EX. Lighter cars go faster than heavier ones pushed with equal force. Lighter cars resist the force of acceleration less allowing them to move faster than heavier ones.

5. 3.3 Newton’s Third Law Newton’s 3rd Law:
For ______ _____ ______ there is a reaction force equal in ________ & __________ in direction
Can be _______ or __________
Examples: rockets, stepping into a boat, throw a ball when on a skate board

6. Net Forces
____ Force - ____ _____ of all the forces that act on an object
In the same _______ – ____ forces together
In ________ directions –_______ forces
largest vector wins when forces act in opposite directions
At right angles (a2 + b2 = c2)
When net Force = 0, there is __ ____________. This means the object is:
Not moving OR
Moving at a constant velocity

7. Gravity, Weight & Mass Gravity- Force ______ toward mass of planet
Depends on _____
Mass- _______ of matter in an object ________ ___ __ ________
Changes on other planets
On Earth= -9.8m/s2
Weight- force ________ by _____, depends on mass
It is a force acting on object in units of lb or N
Fw=mg
Fw= weight force (N)
m=mass (kg)
g=acceleration due to gravity (-9.8 m/sec2) Fw
m g

8. Law of Universal Gravitation
______ __ _________ directly related to masses & indirectly related to distance
F=G m1m2 r2
F= Force of attraction
G= ___________ constant
m1 = mass object 1
m2 = mass object 2
r = radius btw the objects

9. Free Fall-
____ straight down in the ________ of ___ _____________
Acceleration due to gravity _____ m/sec2
Object’s will experience _______ acceleration (uniform increases in velocity) when in _____ ________!
Terminal Velocity-
Highest ________ reached by a ________ object
When an object ______ _________, but continues to fall, terminal velocity is achieved.
Occurs when force of air resistance _________ the weight of the object.

10. What is friction? Friction: _________ acceleration
Works __________ motion
Occurs when surfaces move against one another
Causes _______ on parts
Examples of friction:
_____ friction- (air resistance)- aka – “____”
_______ friction (rub hands together)
________ friction- (oil in car engines & joint fluid)
________ friction- (wheel on road, ball bearings)

11. Static Friction (Ffs) Sliding Friction (Ffk)
The frictional force that must be ________ to get an object moving (Ffs)
μs = Ffs FN
μ=coefficient of friction (ratio of frictional forces to the normal force)
Fw: Weight Force
= mass(gravity)
FN: Normal Force
Often = to the Weight Force (Fw)
The frictional force that ______ once an object is in motion (Ffk)
AKA kinetic friction
μk = Ffk FN

12. Free-body diagrams
It is a diagram that visually represents the various forces being applied on an object:
Fstatic = _______ force (Ff)
Fpush = _______ force (FA)
N = the ______ or support force (FN); perpendicular to surface
W = _____ of object (FW)
The sum of all of the forces involved is called the FNET or FR ( the “R” stands for ____________ or the result of all forces)

13. Rules of Friction
Fp or Fa Ff
If an object is slowing down or not moving, then the frictional force (Ff) is _________ the pulling force
If an object is moving at a constant speed, then the frictional force (Ff) is _____ __ the pulling force
If an object is speeding up, the frictional force (Ff) is _____ _____ the pulling force.
Fp=pulling force = Fa=applied force