Motion

1
Motion
2
The answer is D.

• Average speed is defined as distance traveled
  divided by the time required for the trip.
• Speed v distance / time
• Therefore, an acceptable unit would be any
  measure of length over any unit of time.
• Miles/hour, km/hr, and m/s are the most common
  units

3
Motion
4
The answer is B.

• Acceleration is defined as the change in velocity
  divided by the time it took to change the
  velocity.
• Acceleration a ?v / ?t
• Acceleration tells me how fast an object is
  getting faster (or slower)

5
Motion
6
The answer is E.

• Speed distance / time
• Speed 240 km / 4 hr
• Speed 60 km/hr

7
Newtons Laws
8
The answer is D.

• Newtons first law states that an object tends to
  retain its current state of motion unless acted
  on by a net force.
• This is sometimes referred to as the Law of
  Inertia.
• More massive objects have more inertia because
  they are better at resisting changes in motion
• There was not enough friction to move the milk
  carton with the paper.

9
Newtons Laws
10
The answer is A.

• Weight is the force that an object experiences
  due to gravity.
• Newtons second law states that force is
  proportional to mass and acceleration
• F m a
• The acceleration due to gravity on the moon is
  less than that on earth, therefore the object
  will have a smaller weight
• People often confuse mass and weight. Notice
  that the object had the same mass, or amount of
  matter, on both the earth and the moon

11
Newtons Laws
12
The answer is D.

• Friction is the force that exists between
  contacting objects moving past one another.
• It is caused by interactions between the objects
  on a microscopic scale, as in the diagram below.
• Friction on an object is always opposite the
  direction of the objects motion.

13
Momentum
14
The answer is A.

• Momentum is defined as the product of an objects
  mass and velocity.
• Momentum p mass velocity
• The units are typically kg m/s
• Since the trucks have the same velocity, the one
  with the larger mass has a larger momentum

15
Momentum
16
The answer is A.

• p m v
• v p / m
• v (12 kg m/s) / (4 kg)
• v 3 m/s

17
Work
18
The answer is C.

• Work is defined as force times the distance over
  which the force acts.
• Work W F d
• Since there was 2 times as much force and 2 times
  as much distance
• W 2F 2d
• W 4 (F d)
• The amount of work she did increased by a factor
  of 4

19
Energy
20
The answer is E.

• Kinetic energy is the energy due to motion
• Potential energy is stored energy
• The pendulum is at rest at the top of the swing
  so it has no kinetic energy, but lots of stored
  gravitational potential energy
• At the bottom of its swing,it has no potential
  becausethe potential energy has been converted
  to kineticenergy (it is moving fast!)

21
Simple Machines
22
The answer is D.

• Mechanical advantage roughly tells you how much a
  machine multiplies the force you apply.
• MA output force / input force
• Nothing is free!! The trade-off is that you
  apply the small force over a large distance to
  apply the large output force over a small
  distance (think about a wrench or a ramp)
• The amount of work (W F d) remains relatively
  constant with any loss due to friction

23
Heat Transfer
24
The answers are A then B.

• Conduction is the transfer of energy as particles
  and molecules collide with each other, as in they
  have to touch.
• Convection is the bulk movement of heated or
  cooled material within a sample, as in warm air
  rising and cool air sinking.

Convection currents in boiling water
conduction
25
Heat Transfer
26
The answer is C.

• Electromagnetic radiation is emitted by the sun,
  some of which encounters the Earth, adding energy
  to the matter of the Earth
• Radiation is the transferof energy by
  emittingelectromagnetic rad.which is then
  absorbedby another object

27
Phase Changes
28
The answers are E then B.

• A phase change is accompanied by the absorption
  or release of energy
• A diagram for water with common phase change
  terms is provided below.

29
Waves
30
The answer is C.

• Wavelength is the distance from crest to crest or
  trough to trough, measured in meters.
• Amplitude is the size of the disturbance, from
  center to peak or center to trough
• Frequency is how many time the disturbance occurs
  per unit time, typically in cycles per second or
  Hertz

31
Waves
32
The answer is D.

• Sound is a mechanical wave, meaning that it
  requires a medium, or matter, in order to
  propagate (travel)
• Electromagnetic waves do not need a medium to
  travel. E-mag waves from the sun travel to
  Earth through the near-vacuum that is outer
  space!

33
Waves
34
The answer is C.

• Waves travel at a certain speed. Wavelength and
  frequency are related to speed.
• Wave speed frequency wavelength
• Electromagnetic radiation travels at the speed of
  light, c (3 x 108 m/s), and the sun is so far
  away that it takes almost 8 minutes to reach the
  Earth.
• Mechanical wave speed depends on the matter it is
  traveling in. Sound is faster in solids than
  liquids and slowest in gases.

35
Light
36
The answer is D.

• Our eyes interpret the frequency of light as
  color.
• Because frequency is related to wavelength by
  speed, another acceptable answer could be
  wavelength! But that was not one of the choices
  here.

37
Light and Color
38
The answer is D.

• The primary colors of light are red, green and
  blue
• Red and green light make yellow
• Blue and red make magenta
• Blue and green make cyan
• R, G and B combine to make white
• Hence, a primary color and itscomplement will
  create white
• Colors opposite each otheron the wheel here
  produce white

39
Electric Charge
40
The answer is B.

• Charges that are of similar sign,
  negative/negative or positive/positive, will
  repel each other
• Charges of opposite sign will attract

41
Electricity
42
The answer is E.

• According to Ohms Law, voltage is the product of
  current and resistance
• Voltage V I R
• I is the symbol for current and R is the symbol
  for resistance
• In this problemV I RV 5 A 10 ohmsV
  50 Volts

43
Electricity
44
The answer is E.

• A complete circuit needs a voltage source (like a
  battery), wires to connect all of the components,
  and a load to consume the energy (such as a light
  bulb, or your iPod!)

45
Electric Circuits
46
The answer is B.

• For resistors in series, simply add the
  resistances together to determine total
  resistance
• For parallel circuits, the inverse of the total
  resistance is equal to the sum of the inverses of
  each resistor (see eqn.)
• This problem was a series circuitRtot R1
  R2Rtot 3 ohms 6 ohmsRtot 9 ohms

series
parallel