Physics Fun:

GENERAL
INFO PACKET!

The Study of Mechanics, Energy, Force & Motion

Motion

There
are two basic types of motion. Motion that is uniform and accelerated

motion.

For
an object moving with uniform motion, the velocity remains in the same

direction
and has constant magnitude (size). For uniform motion, forces are

balanced.
There are no net or resulting forces. Under these conditions calculating

the
velocity is straightforward.

velocity
= __distance traveled__
= __ s__ or d

time of travel
t

This
velocity is an average for the trip.

As
soon as forces that do not cancel each other out act on an object, uniform
motion

no
longer takes place. Whenever an unbalanced force acts on an object an

acceleration
is produced. Newton’s second law of motion expresses the relationship

among
force, mass, and acceleration as F = ma.

Force = mass x acceleration
or
acceleration = __Force __

mass

The
acceleration of an object increases as the amount of force causing the

acceleration
increases. The larger the mass of the object, the larger the force

needed
to produce acceleration.

Acceleration
is the change in velocity over a period of time. (How fast something is

going
faster.) This change can be in the speed (whether increasing or decreasing), in

the
direction of the motion, or in both.

Acceleration = velocity / time
a = v / t

Acceleration
occurs anytime there is a change in velocity. For objects moving in a

curved
path, velocity is changing even though speed may be constant. Velocity is a

vector
and therefore must have speed and direction. If your direction is changing,

like
on the Rotor, then there is acceleration toward the center of the Rotor. This

acceleration
is called centripetal
acceleration.

centripetal
acceleration = (velocity)^{2 }/ divided by the radius

ac = centripetal acceleration

ac = v^{2} /r
v = velocity

r = radius of the circle

In
the case of an object spinning in a circle, the size of the velocity (speed) is

calculated
by measuring the time for one complete spin and dividing this into

circumference
of the circle.

v = Circumference / time

If
there is an acceleration, there must be an unbalanced force producing it. The
force

causing
the circular motion is called centripetal force (Fc). This force causes the

object
to change direction, thereby creating the acceleration in the same direction

(toward
the center).

As
stated previously;

F = ma

Newton’s
Second Law of Motion must also apply to circular motion.

Therefore: Fc = mac

If
we substitute ( v^{2} / r) in for (ac), we find the equation needed to
calculate

centripetal
force.

Fc = mv^{2} / r

This
force is easy to see and understand if you swing a rubber stopper on the end of

a
string. You can see your hand is producing the force which is transferred
through

the
string to make the stopper follow the circular path. So your hand produces the

force,
which causes the centripetal acceleration.

In
the Rotor, the wall produces the centripetal force. This force keeps you moving
in

a
circular path by providing an acceleration on you toward the center. You, on
the

other
hand, have the impression that there is a force throwing you toward the wall.

This
is very similar to being in an automobile at rest and the driver pushes the

accelerator
to the floor. If the car has a lot of horsepower, you feel like you are being

pushed
back in the seat. In reality, the seat is accelerating you forward. This
“force”

you
feel back against the seat does not really exist. It’s your inertia trying to
keep

you
at rest. The only force is the seat accelerating you. So, in the Rotor, the
force

you
feel out against the wall, called centrifugal force, is a fictitious force. You
are

reacting
to the wall pushing on you!

Generally
speaking, you might think of centripetal force as an action force and

centrifugal
force as a reaction force. Remember, centrifugal force is considered to be

fictitious.
It can only be observed in the accelerated frame of reference.

These
forces are also found on many other rides at Lake Compounce! Any ride which

moves
in a circular or curved path will produce centripetal and centrifugal
forces.

Earth Gravity and G - Forces

Gravity
refers to the force of attraction between objects. All objects exert a

gravitational
force. Any two objects with mass attract each other, and the strength

of
this force depends on the mass of the objects and the distance between
them.

The
larger or more massive the object, the greater the force.

Some
forces can act from a distance without actual contact between the two objects.

We
are accustomed to the gravity of Earth. When you are standing still the force

exerted
on you by the Earth produces your weight. This is also referred to as one
“g”.

Gravity
causes free-falling objects on the Earth to change their speeds at the rate of

9.8
m/s each second. That is a change
in speed of 32 ft/s in each consecutive

second. Therefore, a “g” is a unit of
acceleration equal to the acceleration caused by

gravity. When you feel heavier than normal you
are experiencing a force greater

then
1 g. When you feel lighter than normal you are experiences a force less
than

1
g. You are weightless when you feel no forces (free fall).

On
the roller coaster, when you go down a steep hill, you will get that “light
stomach

feeling”
and will notice yourself lifting off the seat. You have just experienced

weightlessness.
Imagine the shuttle astronauts having this same feeling continually

for
several days. This may give you an idea of why many astronauts have what is

known
as space or motion sickness. While the shuttle is in orbit, it is falling. With

its
tremendous horizontal velocity, as it falls the Earth curves away from it. So
it

never
hits the Earth, it falls in an orbit.

G – Force Information:

Definition:
The ratio produced when the force felt by an object is

divided by the force that the object would feel while

motionless on the Earth’s surface.

Examples
of g- forces:

Shuttle in Orbit 0 g’s

The Moon
.165 g’s

Mars
.38 g’s

Shuttle
Lift Off
3.0
g’s

Sun
28 g’s

Energy Transformations

There
are many energy transformations that occur at Lake Compounce.

The
main energies used to make calculations involve gravitational potential energy

and
kinetic energy. Potential energy is energy that is stored. Kinetic energy is

energy
of motion.

When
an object is lifted from the ground or rest position it acquires potential
energy.

The
amount of energy can be expressed as:

Ep = mgh

where: m = mass (kg)

g = acceleration due to gravity (m/s2)

h =
height above starting position (m)

Energy is measured in units called JOULES.

When
the object drops, the potential energy that it has is changed to kinetic energy

as
the object falls. At the bottom of its fall, the object is moving at its
fastest velocity

which
indicates it has its maximum kinetic energy. This kinetic energy can be

expressed
as:

Ek = 1⁄2 mv^{2}

where:
m = mass (kg)

v
= velocity (m/s)

Conversion
of energy requires that the total potential at the top must be equal to the

total
kinetic at the bottom. If you calculate the potential energy at the top and set
it

equal
to (1⁄2 mv^{2 })the maximum velocity at the bottom can be
calculated.

Work & Power

Work
is produced by a force acting on an object moving through a distance.

Work = Force x distance

W = Fd
where:
W =
work (joules)

F
= Force (newtons)

d
= distance (meters)

Notice
the unit for work (joules) is the same as the units of energy. Energy is the

ability
to do work. If work is done to lift an object, that work reappears as potential

energy.

Power
is the rate of doing work, or how fast work is done.

__work__ __W__ __ Fd__

Power
=
time = t = t

Where;
P
= power (watts)

W = work (joules)

t
= time (seconds)

Power
in watts can be converted to horsepower using the following

conversion:

1 hp = 746 watts

An Angle on Distance

To
determine the height of a ride use a simple “protractor” elevation finder.

Have
one student sight through the straw at the top of the ride.

Another
student reads the angle on the protractor. The angle read

is
then subtracted from 90 degrees.

To
calculate the height of the ride you will also need the distance between the

student
and the ride.

(Remember
to add the height of your eye to the ground.)

1. Cut out
the protractor including the dashed line section.

2. Trace
the protractor part only on a piece of cardboard,

such as the back of a tablet.

3. Glue or
staple the cardboard to the back of the paper protractor.

4. Roll
the top section around a straw and tape.

5. Punch a
hole and tie a 9 inch string of heavy black thread through

the
hole. On the other end tie a metal
nut, washer, or fish sinker.

6. Follow the directions on the page titled “An Angle
on Distance.”

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**
**Vocabulary

acceleration The rate at which velocity changes. This occurs
if there is change in speed or
direction.

centrifugal force A reaction force to centripetal
force, which you feel in a moving frame. This is a fictitious force. When your body responds to an
acceleration you think there is a
force pushing you back.

centripetal force A force acting toward the center which
makes objects turn.

circumference The distant around a circular object.

diameter
The distance across a circle through the center.

force A
push or pull.

frame or
reference Where you are when you make an observation. (eg. Earth frame or
moving frame)

friction
A force which opposes motion between objects in contact.

g
force A multiplication factor
which compares a force to a person’s weight. (eg. 2 g’s is twice your weight)

gravity A force of attraction between objects.

horsepower A unit established for comparison to the power of
a horse. (1 hp = 746 watts)

inertia A
property of matter which resists a change in its current state of motion.

joule A
unit of work and / or energy in the metric system

kilogram
A unit of mass in the metric system. (1000 grams)

kinetic
energy The energy of motion. The energy an object has due to its velocity. KE = 1/2mv2

mass The
amount of matter an object contains. Mass is unaffected by a change in
gravity.

meter The basic unit of
length in the metric system.

momentum A measure of how
lard it is to stop a moving object.
(mass x velocity)

newton A
unit of force in the metric system.

parabola
A curved path of an object moving at right angles to a gravitational
field.

potential
energy Stored energy. The energy an object has due to its position.

Gravitational potential energy = weight x height

power The rate of doing work. (P = work / time)

projectile An object which has been given kinetic energy and
is moving with no self propulsion.

protractor A measuring device which indicates angles in degrees.

radius
The distance from the center of a circle out to the edge.

watt The
unit of power in the metric system. 1 watt = 1 joule / sec.

weight
The force with which an object is pulled toward the Earth; measurement of force
of

gravity

weightlessness A condition in which you feel no forces
acting on you.

work When a force acts on an object causing it to move
through a distance. The amount of
energy gained by an object that’s moved is equal to the work needed to
move it (no friction). Work = Force x distance

**Reference Sheet: **

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