Download Motion

Motion
What is motion anyway?
Motion is a change in position,
measured by distance and time.
 Anything moving is in motion.

Distance
How can I find out how far I’ve gone?
 Distance = speed x time
 If I drove 3 m/s for 10 seconds, how far
have I gone?

3m/s X 10 s = 30 m
What changes motion?
Force!! F = mass x acceleration
 A force is a push or pull that can
change motion



A force can move an object
A force can transfer energy to an object

For example, pushing on a wall doesn’t move
the wall, but energy is being transferred.
Unbalanced Forces
In order for a force to move an object,
there must be unbalanced forces.
 Like tug of war…the winners are pulling
the other team with more force;
therefore the pulling forces are
unbalanced.

How can force affect motion?
Resistance forces (friction or wind) that
oppose motion can slow down motion.
 A force in the same direction can speed
up motion.

Speed
We talk about speed everyday.
 Speed is the distance traveled by a
moving object per unit of time.
 Speed affect the energy of an object.
The faster it moves, the more kinetic
energy it has.
 Speed = distance
time

Kinetic Energy – Energy of Motion
Speed and mass affect the kinetic
energy of an object.
 If two objects are moving at the same
speed, but one object has a greater
mass, then the object with the greater
mass will have more kinetic energy.
 The more mass in an object, the more
force needed to move it.

Velocity
Velocity and Speed are like fraternal
twins- very similar, but with important
differences.
 Velocity is speed in a given direction.



35 mph NORTH
4 km/sec EAST
Which is which?
100 m/s right
 1500 km/s
 65 m/s north
 3000 km/s

Velocity
Speed
Velocity
Speed
Acceleration

Acceleration is the rate of change in speed.
Acceleration = Change in speed (m/s)
Time (s)
 Example: 0 to 60mph in 3s

Example
The race car accelerated from stop to 60
m/s by the finish line. It took the racecar
8.0 seconds to finish. What was the
acceleration?
Original speed = 0, Final speed = 60 m/s,
Time = 8.0 seconds
Acceleration = 60 - 0m/s = 7.5 m/s^2
8.0s
Friction
Friction is a force that opposes motion.
 Can be caused by wind, water, surface
texture, etc.

Resistance Force
Have you ever ridden down the street
on your bike and felt the wind push
against you?
 That’s air resistance!
 Air resistance is the frictional force from
the air that resists forward motion

Momentum
Momentum is the property that a
moving object has because of its mass
and velocity.
 All moving objects have momentum.


Momentum = mass x velocity
Sir Isaac Newton

Isaac is famous for his discovery of
gravity. He is also known for his three
laws that explain all aspects of motion.
Newton’s First Law

An object at rest will remain at rest, and a
moving object will remain at a constant
velocity unless unbalanced forces act on it.
** Inertia- is the term used to describe the
tendency of an object to remain in motion or
stay at rest.
Newton’s Second Law

Motion produced by unbalanced forces.

The units of force are “Newtons”
1 N = 1 kg x m/s
s
1N is the force on a 1kg mass that will
accelerate that mass at 1 m/s2.

Newton’s Third Law

For every action, there is an equal and
opposite reaction.