Transcript Motion, Forces, and Simple Machines

Motion, Forces, and Simple
Machines
1. Average speed is defined as the total distance traveled
divided by the travel time.
*The formula used to calculate average speed is: s=d/t
*To find the distance (d), the formula changes to: d=s x t
2. instantaneous speed is the speed of an object at any instant of
time.
3. Velocity is the speed of an object and its direction of motion
4. acceleration describes how velocity changes with time
Formula:
A = change in
speed/time
5. Force: a push or pull; is measured in newtons;
causes an object to accelerate, and can
change the direction of an objects motion.
Example: Gravity is a pull that all objects exert
on each other
A. Newton’s First Law
States: An object at rest stays
at rest unless an
unbalanced force acts
on it.
*An object moving in a straight
line at constant speed will
continue doing that unless
acted on by a force. This
force is called friction. It is a
force that resists motion
between 2 surfaces that are
in contact. It always acts
opposite to the direction of
motion.
Sir Isaac Newton
* Inertia is the tendency to resist a change in
motion.
* The more mass (amount of matter in an object)
an object has, the greater the inertia.
** Example: A toothpick has less inertia than a
pencil because it has less mass.
B. Newton’s Second Law
* States: A net force changes the velocity of the
object and causes it to accelerate.
*The more mass or inertia an object has, the
harder it is to accelerate.
More mass = less acceleration
** Example: pushing a refrigerator vs. pushing a
grocery cart
C. Newton’s Third Law
• States: Forces always occur
in equal but
opposite pairs. In
other words, for
every action, there is
an equal and
opposite reaction.
** Example: A rocket blasting off
Space Shuttle
Columbia
7. Work and Simple Machines
* A. Work is defined as when a force causes an
object to move in the same direction that the
force is applied. It is measure in
joules.
* To calculate work, we use the following
formula: W = f x d (f = force and d = distance)
* Machines can change the size and direction of
the force.
b. Simple machines: machines that use only one
movement.
**Examples: inclined plane, wedge, screw, lever,
wheel and axle, pulley
c. Compound machines: combination of simple
machines
**Example: can opener (wedge and inclined
plane)
d. Ideal machine: machine where there is no
friction; the work done by the input force is
equal to the work done by the output force.
Types of Simple Machines
A. Pulley
* object with a groove, like a wheel, with a rope
or chain running through the groove.
* Changes the direction of the input force.
* Example: flagpole
B. Lever
* First simple machine ever invented by humans
* Rod or plank that pivots around a fixed point.
The pivot point is called the fulcrum.
*There are 3 types: first class (screwdriver)
second class (wheelbarrow) and third class
(hockey stick)
* A lever can increase force
or increase the distance
over which a force is applied.
* Example: pry bar
C. Wheel and axle
* 2 round objects that are attached and rotate together about
the same axis. The larger object is the wheel and the smaller
object is the axle.
Example: doorknob
d. Inclined plane
* Sloped surface, sometimes called a ramp
* Allows you to lift a heavy load by using less force over a greater
distance
Inclined plane
Example: ramp
Wheel and axle
e. Wedge
* Moving inclined plane with one or two sloping slides
* Changes the direction of the force you apply
* Example: front teeth, knives, axes
f. Screw
* An inclined plane wrapped around a post
* Like a wedge, it also changes the direction of the force you
apply.
* Example: a screw
screw
Log-splitting wedge
ADD THE
INFORMATION FROM
THE NEXT TWO SLIDES
TO BOTTOM OF THE
NOTE TAKING SHEET
Energy
* The ability to do work or cause change
Energy comes in many forms.
There are 2 types of energy that relate to motion:
1. Potential energy - stored energy/energy of position
example: roller coaster at the top of a hill or holding
a ball in your hand
2. Kinetic energy - energy in motion
example: roller coaster going down a hill or dropping
a ball and it bouncing