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 10 4 m = 3 x 10,000 = 30,000 m 3 x m = 3 / 10,000 = 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 10 3 m = 3000 m 3 x m = m

Weight The force of gravity applied to object Equals mass x acceleration due to gravity (g) g = 9.8 m/s 2 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/s 2 equals Velocity / time Accelerating when speeding up, slowing down or changing direction

The calculate acceleration a = (v f – v i ) / 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 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/s 2

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 F net = 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 = F x d 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 = f o / f i

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 Pulley – used to raise a curtain Inclined plane – ramp Wedge – knife edge Screw – spiral stair case Wheel and axle – doorknob

Levers 1 st class (fulcrum in middle)- seesaw 2 nd class (outgoing force in middle)- wheelbarrow 3 rd 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?