Download Forces and Motion Notes

Forces and Motion Notes
Chapter 1 – Motion
Position – the location of an object
Reference point – a location to which you compare other locations
Motion – the change of position over time
Speed – a measure of how fast something moves or the distance something moves in a
given amount of time
Calculating speed
speed = distance / time
s=d/t
Velocity – speed in a specific direction
Vector – a quantity that has both size and direction
Acceleration – the rate at which velocity changes with time
Calculating acceleration - acceleration = final velocity – initial velocity / time
a = vf – vi / t
Chapter 2 – Forces
Force – a push or pull on an object
3 Types of Forces:
1. Contact Force – when one object pushes or pulls another object by
touching it
2. Gravity – the force of attraction between two objects
3. Friction – a force that resists motion between two surfaces that are
pressed together
Net Force – the overall force acting on an object when all forces are combined
NEWTON’S FIRST LAW OF MOTION – “The Law of Inertia” - objects at rest stay
at rest and objects in motion stay in motion with the same velocity unless acted upon by
an unbalanced force
 Inertia – the resistance of an object to a change in the speed or the direction of its
motion. When you measure the mass of an object you measure its inertia.
NEWTON’S SECOND LAW OF MOTION – the acceleration of an object increases
with increased force and decreases with increased mass. Also, the direction in which an
object accelerates is the same as the direction of the force.
 Calculating Force
Force = mass * acceleration
F = ma
a = F/m
m = F/a
 Newton (N) – the standard unit of force. Defined at the amount of force that it
takes to accelerate one kilogram (1 kg) of mass one meter per second per second
(1 m/s2)
 1N = 1 kg * m/s2
 Centripetal Force - any force that keeps an object moving in a circle
NEWTON’S THIRD LAW OF MOTION – states that every time one object exerts a
force on another object, the second object exerts a force that is equal in size and opposite
in direction back on the first object.
 Balanced Forces –
 Action and Reaction –
Momentum – a measure of mass in motion. The product of an object’s mass and
velocity
Calculating Momentum
momentum = mass * velocity
p = mv
Collision – a situation in which two objects in close contact exchange energy and
momentum
Conservation of Momentum – the total momentum of a system of objects does not
change, as long as no outside forces are acting on that system
Chapter 3 – Gravity, Friction and Pressure
Gravity – the force that objects exert on each other because of their masses.
The force of gravity:
 The mass of the objects – the greater the mass of the objects the greater the force
of gravity the masses exert on each other. If one of the masses is doubled, the
force of gravity between the objects is doubled
 The distance between the objects – as the distance between the objects
increases, the force of gravity decreases. If the distance is doubled, the force of
gravity is one-forth as strong as before