Transcript Acceleration and Momentum

Intro to Forces
and Motion
Physical Science
2014
What is a force?
1) Force is a push or pull
2) Force is the capacity to do work
or cause physical change
3) Force= Mass times acceleration
4) A force is that which changes or
tends to change the state of rest or
motion of a body.
Newton’s 3 Laws
1st : An object in motion stays
in motion. An object at rest
stays at rest. Until an outside
force acts upon it.
2nd : F=ma
3rd : For every action, there is
an equal and opposite
reaction.
The Force Equation
F = ma
Force = mass x acceleration
Mass is in kg
Acceleration is in m/s2
Force is in Newtons (N)
Force Equation Example
How much force is needed to
accelerate a 70-kg rider and
her 200-kg motorcycle at 4
m/s2?
F=ma
F=(70-kg + 200-kg) x (4 m/s2)
F=1080 N
Falling Objects
Any two objects falling from
the same distance, released at
the same time, will land at the
same time
Why is this?
Acceleration due to Gravity
Falling objects
accelerate at
9.8m/s2
Therefore,
Weight=m x G
W=m x 9.8m/s2
Air Resistance
The force air
exerts on a
moving object
If there is no force
except for
gravity, all
objects will
accelerate at a
rate of 9.8 m/s2
Air Resistance
This force acts in the opposite
direction to that of the objects
motion
Air resistance pushes up while
gravity pulls down
Air Resistance Example
Classwork:
Everyone must calculate how
much they really weigh in
Newtons.
Conversion factor: 1kg=2.2 lb
Write at the bottom of your
notes.