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# Exam Review PowerPoint PPT Presentation

Exam Review. Semester 2, 2011. Find the force of an object when it hits the ground if it is dropped from 5 meters and has a mass of 5kg. F = m * a 5 x 9.8 = 49. Find the GPE of an object that weighs 65N and is at a height of 4m.

Exam Review

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## Exam Review

Semester 2, 2011

• Find the force of an object when it hits the ground if it is dropped from 5 meters and has a mass of 5kg.

F = m * a

5 x 9.8 = 49

• Find the GPE of an object that weighs 65N and is at a height of 4m.

• Find the GPE of an object with a mass of 35 kg and is at a height of 40m

65 N x 4m = 260 Joules

35 kg x 9.8 x 40m = 13720 J

• Find the KE of an object that has a mass of 6kg and has a velocity of 25 m/s.

• 1875 Joules

• A forward force of 25 N is put on an object. It experiences a resistance force due to friction of 13N.

• What is the net force on the object?

• If the object has a mass of 0.4kg, what rate would it accelerate at?

12 N forward

A = F/m

12/.4 = 30 m/s/s

• Calculate the velocity of waves which have a wavelength of .5m and has a crest pass the observation point every .5 seconds.

• Frequency = 1/.5 = 2

• Velocity = .5 x 2 = 1 m/s

• Forces:

• Friction – brings objects to a rest, many times we try to reduce it, we need it in many cases!

• Gravity – keeps planets in orbit , more when masses are greater, or distances are shorter

• Normal – force of a surface acting on an object

• Applied – force purposely exerted on an object

### Newton’s Third Law of Motion explains why….

• When you stand, you don’t sink into the ground!

• How rockets are launched into space!

• Why when I walk Miss Reece my arm kills afterwards!

### Describe the motion at a-g

• A. at rest.

• B. moving in the positive direction with constant speed

• C. moving in the negative direction and speeding up

• D. moving in the positive direction and slowing down

• E. moving in the positive direction at a constant speed (slow) and then later fast at constant speed

• G. moving with a negative velocity and a positive acceleration

### Describe the motion at points A, B, and C.

B

C

A

• Describing motion:

• A – Positive acceleration at a constant rate

• B- Still positive acceleration, but at a slower constant rate

• C. Negative acceleration at a constant rate

• In the previous picture, where are the forces on the object balanced?

• Where are the forces on the object unbalanced?

• Balanced = NONE!

• Unbalanced = A, B, and C

• What are the three proofs for the Big Bang Theory?

• Abundance of the light elements hydrogen and helium

• Hubble’s law as witnessed by red shift of objects in the universe (ie…the universe is constantly expending)

### FISSION OR FUSION?

• Fission or Fusion?

• Breaks large atoms into smaller ones

• Builds smaller atoms into larger ones

• Releases energy

• Atomic bombs/nuclear power

• Stars & Supernovas

• Fission or Fusion

• Fission

• Fusion

• Both

• Fission

• Fusion

• As you go across the electromagnetic spectrum what happens to the wavelength, energy and frequency?

• All parts of the electromagnetic spectrum travel at what speed (in a vacuum)?

• Electromagnetic waves are transverse/compressional

• Energy increases

• Frequency increase

• Wavelength decrease

• Speed of light

• Transverse

• If the acceleration of an object is 12 m/s/s and the force on the object is doubles, what is its new acceleration?

• If the acceleration of an object is 12 m/s/s and the mass of the object is doubles, what is its new acceleration?

• If the force on an object is 20 N and the mass of the object is reduced by half, what happens the the objects acceleration?

• 24 m/s/s

• 6 m/s/s

• The acceleration will double

F

H

G

• Name the following parts:

• A

• D

• F

• G

• H

• Wavelength

• Amplitude

• Crest

• Trough

• Equilibrium

### Classify the type of heat transfer

• Movement of tectonic plates

• Warming yourself by a fire

• Movement of air in the atmosphere

• Feet on cold tile floor

• Conduction

• Convection

• Convection

• Conduction

### HEAT TRANSFER

This type of heat transfer can occur in a vacuum:

a) Conduction. c) Convection.

The fact that, in general, liquids and gases expand when heated, gives rise to

a) convection currents in fluids due to changing masses.

b) convection currents in fluids due to changing densities.

c) heat transfer by conduction.

d) convection currents in fluids due to constant temperatures.

• B

• B

### Heat Transfer

• is not possible from human beings to their environment.

• does not occur from light bulbs  they are too bright.

• does not require any material between the radiator and the object receiving the radiation.

• none of the above.

Heat energy always flows from

________ to _________

• C

• Hot to cold…..never cold to hot!!

• Calculate the net force on a ball that has a mass of .5 kg and is falling. The object is experiencing an air friction force of 2N. What is the acceleration of the ball?

• F grav = 4.9N

• Net force = 4.9N – 2N = 2.9N

• A = F/m 2.9/.5 = 5.8 m/s/s

### Draw the refracted ray in the following examples:

• A ray of light is approaching a set of three mirrors as shown in the diagram. The light ray is approaching the first mirror at an angle of 45-degrees with the mirror surface. Trace the path of the light ray as it bounces off the mirror. Continue tracing the ray until it finally exits from the mirror system. How many times will the ray reflect before it finally exits?

• Mac and Tosh stand 8 meters apart and demonstrate the motion of a transverse wave on a snakey. The wave can be described as having a vertical distance of 32 cm from a trough to a crest, a frequency of 2.4 Hz, and a horizontal distance of 48 cm from a crest to the nearest trough. Determine the amplitude, and wavelength and speed of such a wave.

• Amplitude = 16 cm (Amplitude is the distance from the rest position to the crest position which is half the vertical distance from a trough to a crest.)

• Wavelength = 96 cm (Wavelength is the distance from crest to crest, which is twice the horizontal distance from crest to nearest trough.

• Speed = 230 cm/s (The speed of a wave is calculated as the product of the frequency times the wavelength.)

• A tennis coach paces back and forth along the sideline 10 times in 2 minutes. The frequency of her pacing is ________ Hz

• .a. 5.0b. 0.20c. 0.12d. 0.083

• Non-digital clocks (which are becoming more rare) have a second hand that rotates around in a regular and repeating fashion. The frequency of rotation of a second hand on a clock is _______ Hz.

• a. 1/60b. 1/12c. 1/2

• d. 1e. 60

• f =10 cycles / 120 s = 0.0833 cycles/s

• f = 1 cycle / (60 s) = (1 / 60) Hz

• While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. This is a clear case of Newton's third law of motion. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus?

• Trick Question! Each force is the same size. For every action, there is an equal ... (equal!). The fact that the firefly splatters only means that with its smaller mass, it is less able to withstand the larger acceleration resulting from the interaction. Besides, fireflies have guts and bug guts have a tendency to be splatterable. Windshields don't have guts. There you have it.

### PE to KE or KE to PE

• A bungee cord begins to exert an upward force upon a falling bungee jumper.

• KE to PE

• PE to KE

• PE to KE

A ball falls from a height of 2 meters in the absence of air resistance.

The spring of a dart gun exerts a force on a dart as it is launched from an initial rest position.

• a. 400 N Up

• b. 200N Down

• c. 20 N Left

### Classify as a transverse or compressional wave

• Sound

• UV light

• Water

• P waves

• Gamma rays

• Compressional

• Transverse

• Transverse

• Compressional

• Transverse

### Classify as a mechanical or electromagnetic wave

• Visible light

• Earthquake waves

• Sound

• EM Wave

• Mechanical

• Mechanical

• EM Wave