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# DESPICABLE PHYSICS

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by

## Candace Le

on 2 April 2014

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#### Transcript of DESPICABLE PHYSICS

The force of gravity can
be considered constant
when the motion over
short distances near Earth's
surface.
But small variations occur in the acceleration

DESPICABLE PHYSICS
Acceleration occurs anytime an object's …
speed increases,

speed decreases, or

direction of motion changes.
Created By: Candace Le
Period One
Describing Motion
Speed
Acceleration
Velocity
Free Fall
Newton's First Law
Newton's Second Law
Newton's Third Law
Mass
Weight
Galileo versus Aristotle
Friction
The Law of Universal
Gravitation
Acceleration in Circular Motion
Projectile Motion
Linear Momentum
Free-falling objects do not encounter air resistance.
All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s/s
Minion
Golf Club

m = 10 kg
m = 1 kg
a =
a =
F

F
m

m
net
net
=
=
10
1
100
10
N
N
kg
kg
a = 10m/s/s
a = 10m/s/s
The dot diagram at the right depicts the acceleration of a free-falling object.
Rate of change of
distance with time.
Speed and direction
of motion.
VECTOR
SCALAR
Speedometers in cars tell us the (instantaneous) speed but not
velocity.

Speed is a measure of the distance an object travels in a given length of time:
Because only a number is given, not a directional term.
average speed =
distance traveled
time elapsed
INSTANTANEOUS SPEED:
CONSTANT SPEED:
speed at a specific instant in time
rate of change of position in which
the same distance is traveled each
second
=
The position of the object at regular time intervals is shown.
The fact that the distance that the object travels every interval of time is increasing is a sure sign that the ball is speeding up as it falls downward.
Example:
states that an object at rest tends to stay at rest; an object in motion tends to stay in motion (with the same direction and speed)
motion (or lack of motion) cannot change without an unbalanced force acting
natural tendency of objects to keep on doing what they're doing
all objects resist changes in their state of motion
"law of inertia"
Example:
acceleration is produced when a force acts on a mass
the greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object)
gives us an exact relationship between force, mass, and acceleration
F= MA
Force= Mass times Acceleration
When the smaller minion applied MORE force he was able to push off the taller minion.
the rate of change of distance with time

first derivative of distance with respect to time.
Average Speed:
Instantaneous Speed:
Average velocity is the rate of change of displacement with time. Since displacement is a vector quantity, then velocity is also a vector quantity. It has both magnitude and direction.
Velocity is not absolute, it is dependent on the observer.
average velocity =
change in position
time elapsed
measured over a non-zero time interval and
represented by the symbol v (overline)
Average velocity:
Instantaneous velocity:

the limit of average velocity as the time interval approaches zero,
the first derivative of displacement with respect to time, and
represented by the symbol v (boldface)
Displacement =
10 feet East
Direction
v=
10 feet East
t
As a vector, it must be stated with both magnitude and direction.

measured over a non-zero time interval and
represented by the symbol a (overline)

the limit of average acceleration as the time interval approaches zero,
the first derivative of velocity with respect to time,
the second derivative of displacement with respect to time, and
represented by the symbol a (boldface)
Instantaneous acceleration:
Average acceleration:
acceleration=
Δt
Δv
From
To
From
To
THE END
Rate at which velocity changes
over time.
the measure of the amount of matter
measure of resistance to acceleration (more generally, mass is a measure of resistance to all sorts of change.)
a scalar quantity associated with matter
The SI unit of mass is the kilogram [kg].
When a system is composed of several objects it is the total mass that matters.
the force of gravity on an object
Derive formula from the free fall thought experiment.
Things that weigh a newton.
Its direction is opposite the relative velocity (or intended velocity).

Dry Friction
The resistive force between clean dry solid surfaces.
Friction is normally synonymous with dry friction.

Viscous Friction
The resistive force between surfaces in relative motion through a fluid (liquids & gases).

Rolling Resistance
The resistive force experienced by rolling objects.
Since rolling does not does not necessarily involve slipping, rolling resistance is not really a form of friction.
the force between surfaces in contact that resists their relative tangential motion.
"Relative tangential motion" is a fancy way to say "slipping".
Projectile motion is a special case of two dimensional motion with constant acceleration.
The force due to gravity moderates linear motion of an object thrown at certain angle to the vertical direction.
The resulting acceleration is a constant, which is always directed in vertically downward direction.
All forces (push or pull) result from the interaction of two bodies. One body exerts a force on another. Newton's Third Law tells us that this force is exactly equal in magnitude and opposite in direction of the force we exert on the crate.
Newton's third law proclaims: to every action there is an equal and opposite reaction.
Action
Reaction
Circular Motion
Tides
Conservation of Energy
gravitational attraction exists between every pair of objects
F=G
m m
r
1 2
2
masses of the two objects
the distance between their centers
gravitational constant
due to gravity with latitude, elevation, and the types if surface material.
The value of the gravitational field at any point is space is equal to the force
experienced by a 1-kilogram mass placed at that point.
linear momentum=mass x velocity
v
mass
Momentum uses the symbol p.
There isn't a
special
unit for momentum.
momentum unit:
kilogram-meter per second
(kg m/s)
.
momentum is a vector quantity
An object can have a large momentum
vector quantity
its magnitude is the straight-line distance between the initial and final locations of the object
its direction is from the initial location to the final location
Displacement
[The acceleration and the velocity point in opposite directions]
[The acceleration and the velocity point in same direction]
Aristotle vs. Galileo
The heavier banana will fall faster than the lighter banana!
The only reason why that happens is because air resistance slows down the lighter banana. If air resistance was reduced, they would fall at the same time!
A push or pull.
As the one-eyed minion
pushes
the other minion away, he
pulls
the banana (from the other minion's hands) towards his mouth.
Although we don't see the force, we are able to see objects behaving in a certain manner.
EXAMPLE:
In many situations there is more than one force on an object..
When two forces of equal size act along a straight line but in opposite directions, they cancel each other.

object
straight/flat surface
2 forces of equal size
Balanced or Unbalanced forces?
Static frictional force
is equal to the force you exert.
When the minion pushes with a large force, the frictional force is large.
Frictional force is small if the minion pushed with a small force.
Centripetal Acceleration

Collisions
is the force that makes a moving object change direction
is not a particular force, but the name given to the net force responsible for circular motion
acts at right angles to the velocity at any instant
is directed toward the center of a circle
When the speed of a circular motion is constant, it's called an uniform circular motion.
Centripetal Force
occurs whenever a moving object changes direction
does not change the speed of an object
acts at right angles to the velocity at any instant
is directed toward the center of a circle

In a circular motion, the velocity is tangential (lies on a tangent to the path), centripetal acceleration and centripetal force point toward the center of a circle. Centripetal acceleration and velocity are always perpendicular while centripetal force and centripetal acceleration are always parallel to each other.
Aristotle
Galileo
path traveled by ball
m
r
v
m = mass of the ball
v = speed of the ball
Centripetal force =
mv
r
2
are periodic rise and fall of sea levels, as seen in a specific location on the shore, which are caused by the gravitational forces from the Moon and Sun that attract the ocean water toward them and away from other areas in the ocean. There are two high and low tides each day. The orientation of the Moon and Sun with respect to the Earth determine when the highest and lowest tides occur, as well as when the moderate tides occur. When the Moon and the Sun are aligned, the combined gravitational pull causes the highest tides. On the other hand, the lowest tides are typically seen at locations which are 90 degrees to the alignment of the Moon and Sun.
Elastic
Inelastic
part of the kinetic energy is changed to some other form of energy in the collision
no loss of kinetic energy in the collision
both conservation of momentum and conservation of kinetic energy are observed
Before:
After:
v
v
1
2
A minion hits the eight ball, which is initially at rest, head-on with the cue ball. Both of these balls have the same mass and the velocities are equal.
Gravitational potential energy
is energy an object possesses because of its position in a gravitational field.
A decrease in one form of energy will result in an increase in another form of energy of equal magnitude.
ΔE1 = −ΔE2
The total energy of a closed system is a constant.
∑Ef = ∑Ei = constant
Energy can neither be created nor destroyed.
1 kg = 1,000 g
Full transcript