Physical Science Final Exam ReviewMiss Glover

Motion•Distance in meters: How far you have

traveled•Velocity in m/s: How fast you are going•Acceleration in m/s2: Rate of change of

velocity- speeding up, slowing down or turning!

Equations:

Constant V AccelerationGraphs: d d

t t

( )d d Vf Vi

v d v t t at v t

Example:

•A truck drives 1000 km in 10 hours, what is it’s speed?

•d=1000km t=10 hours v=?v=d/t=1000/10= 100km/hr• A boat travels for 5 hours at 20 miles per

hour, How far does it go?• t=5 hr v=20mi/hr d=?

d=v(t)=20(5)= 100 mi

Acceleration

•A PR runner accelerates from rest to 10 m/s in 4 seconds, what is her acceleration?

•Vi=0m/s Vf=10 m/s, t=4 sec a=?•A=(Vf-Vi)/t= (10-0)/4= 2.5 m/s/s

Freefall•ALL objects accelerate towards the Earth

at g=10 m/s2 due to the large mass of the

Earth• An object that is accelerating is

increasing velocity at 10 m/s each second downwards, or decreasing the velocity by 10 m/s each second as it goes upwards. • The distance an object goes while

accelerating increases proportional to the time squared.

• EQ:

21 2

2

dVf gt d gt t

g

Projectiles•Combine a constant velocity problem

horizontally, and a free fall acceleration problem vertically (g=10!).

•A ball dropped will hit the ground at the same time as a ball given an initial velocity horizontally.

•The only force acting on a projectile is gravity!

• Horizontal Angle

( ) ( )5 5

d Vyd v t t d Vx t t

Forces- Newton’s Laws• 1st Law: Inertia: An object in motion stays in

motion, and an object at rest stays at rest, UNLESS acted upon by an outside net force.

• 2nd Law: F=ma: A net force causes a mass to accelerate.

• 3rd Law: Action/Reaction: For every force there is an equal and opposite reaction force.

EQ:

AB BA

FF ma a F F

m

Forces•Units of force are Newtons= kg (m/s2)

Defined as a push or a pullSome forces we have considered:•Force of Gravity (Weight) Fg=m(g)=

m(10)m= mass in kg• Force of Friction: A force OPPOSING the

motion of two surfaces over each other. Always in the direction opposite the motion. Can be helpful- like providing traction to a car or Can be a hindrance-may cause your brakes to heat up

Energy•Units of Joules•Potential Energy is energy stored up due

to an objects location in the gravitational field (a height off the ground!)

•Kinetic Energy is energy due to an object’s motion.

•If energy is conserved, the energy at the PE at the top of a tree or coaster will equal the KE at the bottom.

21 2

2

bottomtopPE mgh PE KE

KEKE mv v

m

Work and Power

•You give objects energy (PE or KE) by doing WORK!

•To do work you apply a force over a distance.

•Work will equal the energy you gain, so it also has units of Joules.

•Power is the rate of doing work or the Work/Time

( ) average

WW F d P P mav

t

Work Example

•A force of 20 N is applied to a box to move it a distance of 8 m, how much work is done?

•F=20 N, d=8m, W=?•W=F(d)= 20(8)= 160 J

Simple Machines•Used to reduce or change the direction of

a force needed to do work by increasing the distance over which the force is applied.

•Seven Types: Lever, Pulley, Inclined Plane, Gear, Wheel and Axle, Wedge, Screw

•Simple machines involved just one motion- ramp, door knob, handle etc… two or more simple machines may be combined to make a complex machine like a wheel barrel or a bike!

Simple Machine Calculations

•The ratio of the force you get from a machine compared to the force you need to apply is called the Mechanical Advantage (MA).

•The ratio of the distance you must apply the force compared to the distance the machine applies the force is called the Ideal Mechanical Advantage (IMA)

R E

E R

F dMA IMA

F d

Simple Machines Examples•A lever is used to lift a 10,000 lb car with

a force of 500 lbs, what is the mechanical advantage of the lever?

•Fe=500 lbs, Fr=10,000 lb MA=Fr/Fe•MA= 10000/500 =20 (no units!)

•A inclined plane is 10 feet long and 2 feet tall, what is the Ideal Mechanical Advantage?

•de=10ft, dr=2 ft, IMA=de/dr•IMA=10/2=5 (mo units!)

Momentum

•A object that is moving has momentum! •Momentum (p)= mass (velocity) units:

kg(m/s)•The more mass or velocity an object has,

the more momentum it has. •For a given mass, the faster moving object

will have more momentum.•Force a given velocity, the more massive

object will have more momentum.

Momentum Examples

•Which has more momentum, a 2000 kg car moving at 1 m/s, or a 1 kg mass moving at 2000 m/s?

•p=m(v) so they have the SAME momentum!

•Joe with a mass of 75 kg, runs at 2 m/s during warm-ups and 10 m/s during the race, when does he have more momentum?

•p= m(v) so more velocity, more momentum!

Momentum and Impulse•To change an object’s momentum you

could change its mass or velocity. This can be done by altering the object or applying a force!

•Applying a force over a time is called an Impulse and it will equal the change in momentum.

•Egg drop/Air bags: Extend the time, reduce the force

•Follow through: Extend the time to increase the change in momentum.

( ) ( )f ip mv F t m v v p

Waves

•All waves transport energy through the medium.

•The medium is the material that the wave is passed on through- water, air, glass…

•The wave speed will depend on what medium your are traveling through and equals frequency times wavelength

v f

Types of Waves•Transverse Waves- Particles move

perpendicular to the wave motion. EX: Coil, slinky, guitar string

•Longitudinal Waves- Particles move parallel to the wave motion. EX: Sound, Grab and release slinky coils.

•Transverse and longitudinal NEED a medium!•Electromagnetic Waves- DO NOT need a

medium to be passed on- can travel in a vacuum (empty space)

Parts of a WaveCrests: Top of waveTroughs: Bottom of WavesWavelength: Distance for one full wave- Crest to Crest (A-E) or (E-H)(l)

Compression: High Pressure RegionRarefaction: Low Pressure Region

Wave Behaviors•Reflection- bouncing of a wave off of a

barrier•Refraction-Change in wave speed due to a

change in medium•Diffraction- Bending of a wave around a

barrier

•Interference- Two or more waves going through he same medium at the same time.

Sound

•Sound travels fastest in a solid, slowest in cold air

•The speed of sound depends on the temperature of the air

•The highness or lowness is the PITCH of a sound

•The volume of sound is determine by its intensity

1331 / (.6 / )v f f v m s m s T

T

Electromagnetic Waves•All electromagnetic waves travel at c=3 X

108 m/s•Exhibit all wave behaviours

High frequenc

y

Low frequency

Lenses and Mirrors

•Lenses Refract Light, Mirrors Reflect Light•Real- Light rays actually cross (can focus

on screen)•Virtual- Light rays only appear to cross

(cannot focus on a screen) •Erect- Right side up• Inverted- Upside down•Larger/Smaller- Image size compared to

object

Lenses and Mirrors

•Converging: Convex Lens/Concave Mirror▫Inside the focal point: Larger, Erect, Virtual▫Outside the focal point: Inverted, Real▫Examples: Magnifying glass, telescope,

make up mirror, glasses•Diverging: Concave Lens/Convex Mirror

▫ALWAYS Smaller, erect, virtual▫Examples: Security mirror, glasses

Ray Diagrams

•In parallel, out through the focus•In through the focus, out parallel•Draw an image where the rays meet, or

appear to meet.•Describe the image as

Real or VirtualErect or InvertedLarger or Smaller

Ray Diagrams