1. Forces, Waves and Electricity 26%

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. 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

4. Sample Question #1
Use the equations for velocity and acceleration to solve the following examples:
A ball rolls in a straight line very slowly across the floor traveling 1.0 meter in 2.0 seconds. Calculate the velocity of the ball.
Answer: v = 0.50 m/s
If the ball from the above question rolls to a stop in 2.0 seconds, calculate the acceleration (deceleration) of the ball.
Answer: a = m/s2

5. Newton’s 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

6. Newton’s 2nd Law of Motion
Force = mass x acceleration
F = ma

7. Newton’s 3rd Law of Motion
For every action, there is an equal but opposite reaction
Examples:
Punch a wall, it punches back
Rocket propulsion

8. Mass- stays the same Weight- changes gravity decreases, weight decreases
Mass is in g, kg
Weight is is Newtons

9. Falling objects and gravity
Force, mass, and acceleration are interdependent.  A change in any one of these affects the others.
Friction is an ever present force that opposes motion.
All objects fall at the same speed independent of its mass if there are not frictional forces acting upon them.

10. Falling objects and gravity
An astronaut on the moon drops a feather and a rock from the same height. They reach the ground at the same time. Why does this happen on the moon but NOT on Earth?
The moon has no atmosphere.
The moon’s weaker gravity pulls each with less force.
Objects dropped on Earth are not influenced by lunar gravity.
On Earth, the rock has more mass due to Earth’s stronger gravity

11. where force and distance are in same direction
Energy and Work
Energy = 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(J)

12. Static Equilibrium
If the combined effect of all the forces acting on a body is zero and the body is in the state of rest then its equilibrium is termed as static equilibrium.    

13. 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

14. Types of Mechanical Energy
Kinetic = energy of motion
Potential = stored energy due to position

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

16. Electromagnetic Wave (EM) versus Mechanical Wave
EM WAVE
does not require matter to transfer energy
CAN travel through a vacuum
example: light
MECHANICAL WAVE
does require matter to transfer energy
CANNOT travel through a vacuum
example: sound

17. A scientist investigates the type of radiation being emitted by a radioactive sample. An apparatus is constructed using a radiation detector, a radioactive sample, and two different types of absorbers placed between the detector and the sample.
Absorber used Average counts per second
No absorber 33
Paper 1 mm thick 20
Metal 3 mm thick 1

18. Question Which type(s) of radiation does the sample emit?
A. The sample emits alpha radiation.
B. The sample emits beta radiation.
C.*The sample emits both alpha and beta radiation.
D. The sample emits neither alpha nor beta radiation.

19. vacuum of space
Light but NO sound

20. Speed of Sound
empty
space
gas
none
slowest
liquid
solid
fastest

21. Light faster than Sound Thunder & lightning L then T
thunder and lightning
L then T
Light faster than Sound
Thunder & lightning
L then T
Light faster than sound
Thunder

22. Reflection of Light When light strikes a boundary, it reflects.
The angle at which the wave approaches a flat reflecting surface is equal to the angle at which the wave leaves the surface (like a bounce pass of a basketball).
Reflection results in image formation.

23. 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

24. refraction

25. Wave Interference
the phenomenon which occurs when two waves meet while traveling along the same medium
constructive = waves add to produce a larger wave
destructive = waves cancel to produce a smaller wave
CONSTRUCTIVE
DESTRUCTIVE

26. This diagram shows two overlapping waves with the same wavelength and amplitude.
Which statement correctly explains the diagram?
A. The waves overlap and increase in frequency.
B. The wave frequencies overlap and increase refraction.
C. Diffraction between the waves increases the amplitude.
D. Interference between the waves increases the amplitude.

27. Which diagram represents interference?

28. incoming departing Increase frequency, Decrease frequency
Doppler Effect
Increase frequency, Decrease frequency
incoming
departing

29. Electricity Electrons carry a negative charge.
Lost electrons = positive charge
Gained electrons = negative charge
REMEMBER:
Like charges repel
Opposites attract

30. Ohm’s Law and electricity
In a direct current (DC) circuit, the relationship between the current (I) passing through a resistor, the potential difference (V) across the resistor, and the resistance (R ) of the resistor is described by Ohm’s Law:
V = IR.
Find this formula
On your
Formula Sheet

31. Direct Circuits (DC)
The "I" is thought to have been meant to represent "Intensity" (of electron flow)
Free electrons tend to move through conductors with some degree of friction, or opposition to motion. This opposition to motion is more properly called resistance
The force motivating electrons to "flow" in a circuit is called voltage. Voltage is a specific measure of potential energy that is always relative between two points

32. What is the amount of voltage provided by the battery?
V= IR V= (2A) X V=14

33. Practice What formula do you use? How many volts is in this circuit?
How many Ohms?
How much current?

34. Electrical Circuits Current flows in a closed circuit Ohm’s Law
V = IR
Two types of circuits:
Series (single path)-Christmas tree lights
Parallel
(many paths)-houses
SERIES
PARALLEL

35. Permanent Magnets

36. ELECTROMAGNET
Stronger: more loops
stronger battery

37. “Mag”nificent Information
Even the most powerful permanent magnet is not as strong as the stronger electromagnets, so their applications are limited, but they still have many uses.
Magnets can be found everywhere, including your computer, ATM and credit cards, speakers and microphones, electric motors, and toys.
Electric motors work through an interaction between an electromagnet and a permanent magnet .

38. Waves – Electricity Hertz – frequency
Volts- Potential Difference Voltage V
Amps- Current A
Ohms- Resistance Ω

39. 1.WRITE DOWN WHAT YOU KNOW BEFORE YOU START!!!!
Remember to….
1.WRITE DOWN WHAT YOU KNOW BEFORE YOU START!!!!
2.Take your time
3.Guess if you need to