Physics GHSGT Review

1
Physics GHSGT Review
2
Speed and Velocity

• Speed distance divided by time
• s d/t
• Units of speed m/s
• Velocity speed in a given direction
• Example
• 55 mph speed
• 55 mph north velocity

3
Distance versus Time Graph

• AKA position versus time graph
• Straight line represents constant (uniform) speed

4
Acceleration

• Acceleration rate at which velocity changes
• Involves a change in speed OR direction
• a (vf vi )/ t
• Units of acceleration m/s2
• Example 0 to 60 mph in 5 seconds
• For acceleration to occur a net (unbalanced)
  force must be applied

5
Distance versus Time Graph Revisited

• Non-linear graph represents acceleration
• Parabola constant acceleration

6
Forces

• Force a push or a pull
• Net Force sum of all forces acting on an object
• Free-body diagram shows all forces with vector
  arrows
• Direction of force direction of acceleration
• Friction is a force that always opposes motion

7
Determining the Net Force
8
Newtons 1st Law of Motion

• An object at rest will remain at rest and an
  object in constant motion will remain in constant
  motion unless acted on by an unbalanced force.
• Reason for seatbelts

9
Newtons 2nd Law of Motion

• Force mass x acceleration
• F ma

10
Newtons 3rd Law of Motion

• For every action, there is an equal but opposite
  reaction
• Examples
• Punch a wall, it punches back
• Rocket propulsion

11
Gravity

• Gravity attractive force between two objects
  that have mass
• Depends on mass and distance

12
Effects of Mass and Distance on Gravity
13
Momentum

• Momentum is mass in motion
• p mv
• To change an objects momentum a force must be
  applied
• Conservation of momentum states that momentum
  before a collision equals momentum after

14
Energy and Work

• The ability to do work
• Work transfer of energy by applying a force to
  move an object
• W Fd
• where force and distance are in same direction
• Both work and energy are measured in Joules

15
Examples of Work and No Work

• Hammer applies a force to move the nail in the
  same direction WORK
• Waiter applies a force upward while the tray
  moves forward NO WORK

16
Types of Mechanical Energy

• Kinetic energy of motion
• Potential stored energy due to position

17
Conservation of Energy
18
Conservation of Energy
19
Conversion of Energy

• Motor converts electrical energy into
  mechanical energy
• Motors make fans Move which is Mechanical
• Generator converts mechanical energy into
  electrical energy
• Georgia Power use a Generator to provide
  electricity

20
Power

• Power rate at which work is done
• P W/t
• Measure in Watts
• More work, less time More Power
• Less Work, Long time Less Power

21
Heat Energy

• Heat can be transferred through
• Conduction when objects touch
• Convection when matter moves
• Radiation in the form of waves
• Conductors easily transmit energy
• Example metals
• Insulators do not easily transmit energy
• Example gases such as air

22
Light

• Light is a form of electromagnetic radiation (EM)
• EM spectrum shows the forms of radiation in order
  of increasing frequency and decreasing wavelength

23
Energy of a Wave

• The energy transferred from a vibrating source is
  carried by a disturbance in the medium, not by
  matter moving from one place to another.
• Waves move ENERGY, not matter
• Energy carried by a wave consist of KE and PE

24
Parts of Wave

• The dashed lines represent the equilibrium
• The crests are the highest parts of the wave
  (letters A and F)
• The troughs are the lowest parts of a wave
  (letters D and I)
• Wavelength is the distance from crest to crest (A
  to F) or trough to trough (D to I)
• Amplitude is the distance from the midpoint to
  the crest

Wavelength
crest
trough
Wavelength
25
Transverse Waves

• Transverse wave a wave with a vibration at
  right angles to the direction the wave is
  traveling.
• The energy moves through the medium left to
  right, but the motion of the wave is up and down
• Makes an S shape wave
• Ex light waves, string instrument

26
(No Transcript)
27
Longitudinal Waves

• Longitudinal wave a wave in which the vibration
  is in the same direction as that which the wave
  is traveling.
• Both the energy motion and the movement of the
  wave are left to right
• Makes a pulse through the wave
• Ex sound waves, earthquake waves

28
(No Transcript)
29
Doppler shift

• The doppler shift a a change in frequency of a
  wave based on the movement of the observer or the
  source
• Ex a siren changing pitch as it moves towards
  or away from you
• http//www.colorado.edu/physics/2000/applets/doppl
  er2.html
• http//www.colorado.edu/physics/2000/applets/doppl
  er.html

30
A Sound Wave

• Sound waves are longitudinal waves.
• Parts of a sound wave
• 1) Compression areas of high pressure
• 2) Rarefaction areas of low pressure
• As a source vibrates in a periodic fashion, a
  series of compressions and rarefactions is
  produced
• For all wave motion, it is not the medium that
  travels across the room, but a pulse (or energy)
  that travels.

31

• The speed of sound varies in different media. In
  general, sound is transmitted faster in liquids
  than in gases, and still faster in solids.
• Remember that sound DOES NOT travel through a
  vacuum

32
The EM Spectrum

• All of the EM waves are the same in nature,
  differ only in the wavelength and frequency
• Ronald McDonald Is Very Ugly X-tra Gross

33

• The speed of light is constant when it travels
  through one type of medium.
• Light travels faster in air than in water.
• Molecules in its way slows light down
• It is the opposite of sound waves, which require
  a medium to move faster
• Light travels the fastest in a vacuum and slowest
  in a solid
• The more molecules in its way, the slower it goes
• Vacuum gt G gt L gt S

34
Color of Light

• We see different colors depending on the
  frequency of light emitted or reflected
• This is the reason blue flames are hotter than
  yellow. Blue has a higher frequency so more
  energy.

35
Mixing Colored Light

• Light of all the visible frequencies mixed
  together produces white light.
• White light can also be produced by mixing red,
  blue, and green light.
• Red, blue, and green are the 3 primary colors of
  light.
• Color T.V.s produce all the colors we perceive by
  combining red, blue, and green light in a variety
  of ways.

36
Adding Primary Colors

• Red Green Yellow
• Red Blue Magenta (Purple)
• Blue Green Cyan (Aqua)
• Red Blue Green White

37
Refraction of Light

• Light waves travel faster in air than in water
  and slower in glass than water.
• More dense slower light
• When light enters a different medium, speed
  changes and it bends.
• Bending of light due to change in speed
  REFRACTION

38
Electricity

• Electrons carry a negative charge.
• Lost electrons positive charge
• Gained electrons negative charge
• REMEMBER
• Like charges repel
• Opposites attract
• An object can be charged through
• Friction (rubbing two objects together)
• Conduction (touching a charged object to an
  uncharged object)
• Induction (holding a charged object near an
  uncharged object)

39
Electrical Circuits
SERIES

• Current flows in a closed circuit
• Ohms Law
• V IR
• Two types of circuits
• Series (single path)
• Parallel (poly paths)

PARALLEL
40
Electromagnet

• One can make an electromagnet with a nail,
  battery, and wire
• When current flows through the coiled wire, the
  nail becomes magnetized.

41
Electromagnetic Induction

• Occurs when a current is produced by moving a
  conducting wire through a magnetic field

42
Radioactive Half-Life

• Half-life The time required for half of the
  atoms of a radioactive isotope of an element to
  decay.
• Radioactive isotopes decay at different rates
• The amount of a substance halves every half-life
• Ex If the half life of an isotope if 10 years,
  then after 10 years there is only half left.
  After 20 years, there is only half of that half
  (or 1/4th left)