Transcript Physical Science Review - elyceum-beta

Physical Science Review
Physics
Get out
• Paper
• Write the notes you think are necessary
• Working on chps 1,10,11,12
• Will be continued Thursday and Friday
Scientific notation
• 3 x 104 m = 3 x 10,000 = 30,000 m
• 3 x 10-4 m = 3 / 10,000 = 0.0003 m
Basic measurements
• Length – meters
• Mass- the amount of matter in an object,
measured in kg
• Time – seconds
• These are SI-units (international standards)
Metric prefixes
• 1 kilogram = 1000 grams
• 100 centimeters = 1 meter
• 1 second = 1000 milliseconds
Metric conversions
• 245 cm = ________ m
• 34.5 kg = __________ g
Scientific notation
• 3 x 103 m = 3000 m
• 3 x 10-3 m = 0.003 m
Weight
• The force of gravity applied to object
• Equals mass x acceleration due to
gravity (g)
g = 9.8 m/s2 on Earth
Kinematics
• The study of how things move
Measuring length
• Displacement – difference between start
and finish position (Magnitude and
Direction)
• Distance – Length of path (magnitude, no
direction)
Measuring how fast
• Velocity – rate of motion
– Displacement / time (direction counts)
• Speed – rate of motion
– Distance/ time (no direction)
Both have units of m/s
Calculate constant velocity
v=d/t
*Relative motion
• Speed based on comparison to objects or
features in environment
• Ex: Person walking down aisle of a moving
bus
Acceleration
• Rate of change in velocity
• m/s2
• equals Velocity / time
• Accelerating when speeding up, slowing
down or changing direction
The calculate acceleration
• a = (vf – vi) / t
What is acceleration of a car that starts
from rest and reaches 5.3 m/s in 13
seconds?
Questions
• What is the difference between distance
and displacement?
• What is the difference between an object
accelerating versus moving at a constant
velocity?
Uniform circular motion
• An object moving at a constant speed
around a circular path.
• Object undergoes acceleration due to
change of direction
Position-Time graphs
• Walking in the courtyard
• Also called distance-time graphs
• Relate shape of graph to type of motion
– Stopped, forward, backward
– Constant velocity, speed up, slow down
– Acceleration vs. constant velocity
P- T graphs, part 2
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Horizontal line
Sloped line
Vertical line
Curved line
Describe the P-T graph
V-T graphs will be on test for on
honors
• Numbers represent how fast an object is
going, not its location
What motion do these represent?
• Horizontal line
• Sloped line
• Vertical line
• Curved line
Velocity-time graphs
• May also be called speed-time graphs
• How is backward motion indicated?
Forces
• Any push or pull on an object
• Units are Newtons = kg m/s2
Frictional force
• Related to- Roughness of surfaces and
the force pushing surfaces
• Force is opposite to direction of motion
• Can not make object move
Air resistance
force of the air that pushes against a
moving object
force direction is always opposite motion
direction
Unbalanced vs balanced forces
• Unbalanced force: forces in one direction
is more than those in the opposite
direction
• Balanced force:
– Forces are equal but in opposite direction
– equilibrium
Inertia
• The resistance of an object to change in motion
• Based on mass
• The object with the greater inertia requires more
force to alter its rate of motion
• Which object on your desk top has the most
inertia?
Newton’s First Law
• An object at rest will stay at rest, an object
in motion will stay at the same motion,
unless acted upon by a net outside force
Newton’s Second Law
• Fnet = ma
Newton’s Third law
• For every action, there is an equal and
opposite reaction
Situation
• A track star pushes off a block with their
foot to begin the 100 meter dash.
• Find a connection between all 3 laws and
the situation described above
Net force
• The sum of all forces on an object
Normal force
• Equal to the reactive force of the ground
pushing back on object
• Provide a example from the room of a
normal force
Free fall
• An object accelerating only due to gravity
Terminal velocity
• When the gravitational force is balanced
by the force of air resistance
• An object at terminal velocity, the object
stops accelerating downward
*Free body diagrams
• A drawing showing how forces are applied
to an object
• Object is represented by a dot
• Forces are represented by arrows pointing
away from dot
Draw a free-body diagram
• Of an sky diver at terminal velocity
• Of a baseball getting hit by a bat on a
windy day
Momentum
• Equals an objects mass times its velocity
• P=mv
• Inertia in motion, pain index of impacts
• Which has more momentum, a parked car,
a runner, an airplane moving at 100 m/s
Change of momentum
• Momentum only changes if a net force is
applied to object
• Velocity is the easiest value to change
Auto accidents
• Is the change of momentum of the driver
the same, greater or less
if an air bag is used to stop the forward
motion of the driver?
Automobile Accidents and change
in momentum
• Safety features include, air bags, padded
steering wheel and dashboard, crumple
zones, seat belts
• All safety features
– can NOT alter the size of the change in
momentum
– but EXTENDS the time the change takes
place, lowering force applied
Conservation of momentum
• Momentum can be transferred to another
object upon impact
• Momentum is not created or destroyed
• Mr. Baker shooting a gun, what is the sum
of the momentum of both the gun and
bullet before and after the shooting?
Work
• Ability of a force to move an object
• W=Fxd
• Joules
• Force and motion must be in same
direction
Power
• The rate of doing work
• P = W/t
• Watts
Mechanical advantage
• The ratio of the amount of force got from
machine to force put into machine
• MA = fo / fi
Simple machines advantages
• 1) Mechanical (force) advantage (more
force out of machine than put in)
• 2) direction change
• 3) more distance out is than distance in
using machine
Simple machines
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Pulley – used to raise a curtain
Inclined plane – ramp
Wedge – knife edge
Screw – spiral stair case
Wheel and axle – doorknob
Levers
• 1st class (fulcrum in middle)- seesaw
• 2nd class (outgoing force in middle)wheelbarrow
• 3rd class (incoming force in middle)
• Broom
Compound machine
• Machine made out of 2 or more simple
machines
• scissors
Energy
• The ability to do work
• The amount of work done = energy
expended
• Joules
Energy types
• Potential – stored energy
– GPE – energy of position
– EPE – energy of deformation
• Kinetic energy – energy involved with
motion
• Mechanical energy = sum of potential and
kinetic energy
Law of conservation of energy
• Energy can not be created or destroyed,
only transferred /transformed
Roller coasters
• Where would the car have the most GPE?
• Where would the car have the most KE?
• TE?