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. Find the force.

Exam ReviewExam ReviewSemester 2, 2011Semester 2, 2011

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

F = m * a

5 x 9.8 = 49

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

Find the GPE of Find the GPE of an object with a an object with a mass of 35 kg and mass of 35 kg and is at a height of is at a height of 40m40m

65 N x 4m = 260 Joules

35 kg x 9.8 x 40m = 13720 J

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

1875 Joules1875 Joules

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

What is the net force on the What is the net force on the object?object?

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

a.a. 12 N forward12 N forward

b.b. A = F/m A = F/m

12/.4 = 30 12/.4 = 30 m/s/sm/s/s

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

Frequency = 1/.5 = 2Frequency = 1/.5 = 2

Velocity = .5 x 2 = 1 Velocity = .5 x 2 = 1 m/sm/s

Forces:Forces: Friction – brings objects to a rest, many times Friction – brings objects to a rest, many times

we try to reduce it, we need it in many cases!we try to reduce it, we need it in many cases! Gravity – keeps planets in orbit , more when Gravity – keeps planets in orbit , more when

masses are greater, or distances are shortermasses are greater, or distances are shorter Normal – force of a surface acting on an objectNormal – force of a surface acting on an object Applied – force purposely exerted on an objectApplied – force purposely exerted on an object

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

When you kick your wall with your foot, When you kick your wall with your foot, your foot hurts!your foot hurts!

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

How rockets are launched into space!How rockets are launched into space!

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

Describe the motion at Describe the motion at a-ga-g

A. at rest.A. at rest.

B. moving in the positive direction with constant speedB. moving in the positive direction with constant speed

C. moving in the negative direction and speeding upC. moving in the negative direction and speeding up

D. moving in the positive direction and slowing downD. moving in the positive direction and slowing down

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

G. moving with a negative velocity and a positive G. moving with a negative velocity and a positive accelerationacceleration

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

A

B

C

Describing motion:Describing motion: A – Positive acceleration at a constant rateA – Positive acceleration at a constant rate B- Still positive acceleration, but at a slower B- Still positive acceleration, but at a slower

constant rateconstant rate C. Negative acceleration at a constant rateC. Negative acceleration at a constant rate

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

Where are the forces on the object unbalanced?Where are the forces on the object unbalanced?

Balanced = NONE!Balanced = NONE!

Unbalanced = A, B, and CUnbalanced = A, B, and C

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

Abundance of the light Abundance of the light elements hydrogen and elements hydrogen and heliumhelium

Cosmic Background Cosmic Background RadiationRadiation

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

FISSION OR FUSION?FISSION OR FUSION?

Fission or Fusion?Fission or Fusion? Breaks large atoms Breaks large atoms

into smaller onesinto smaller ones Builds smaller atoms Builds smaller atoms

into larger onesinto larger ones Releases energyReleases energy Atomic Atomic

bombs/nuclear bombs/nuclear powerpower

Stars & SupernovasStars & Supernovas

Fission or FusionFission or Fusion FissionFission

FusionFusion

BothBoth FissionFission

FusionFusion

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

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

Electromagnetic waves Electromagnetic waves are are transverse/compressional transverse/compressional

Energy increasesEnergy increases Frequency increaseFrequency increase Wavelength decreaseWavelength decrease

Speed of lightSpeed of light

TransverseTransverse

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

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

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

24 m/s/s24 m/s/s

6 m/s/s6 m/s/s

The acceleration will The acceleration will doubledouble

Name the following Name the following parts:parts:

AA DD FF GG HH

WavelengthWavelength AmplitudeAmplitude CrestCrest TroughTrough EquilibriumEquilibrium

F

GH

Classify the type of heat Classify the type of heat transfertransfer

Rubbing your hands Rubbing your hands togethertogether

Movement of tectonic Movement of tectonic platesplates

Warming yourself by a fireWarming yourself by a fire

Movement of air in the Movement of air in the atmosphereatmosphere

Feet on cold tile floorFeet on cold tile floor

ConductionConduction

ConvectionConvection

RadiationRadiation

ConvectionConvection

ConductionConduction

HEAT TRANSFERHEAT TRANSFER

This type of heat transfer can This type of heat transfer can occur in a vacuum:occur in a vacuum:

a) Conduction. c) Convection.a) Conduction. c) Convection.b) Radiation. d) Blackbody.b) Radiation. d) Blackbody.

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

a) convection currents in fluids a) convection currents in fluids due to changing masses.due to changing masses.

b) convection currents in fluids b) convection currents in fluids due to changing densities.due to changing densities.

c) heat transfer by conduction.c) heat transfer by conduction.d) convection currents in fluids d) convection currents in fluids

due to constant temperatures.due to constant temperatures.

BB

BB

Heat TransferHeat Transfer

Heat transfer by radiationHeat transfer by radiation

a)a) is not possible from human is not possible from human beings to their beings to their environment.environment.

b)b) does not occur from light does not occur from light bulbs bulbs they are too bright. they are too bright.

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

d)d) none of the above.none of the above.

Heat energy always flows Heat energy always flows fromfrom

________ to _________________ to _________

CC

Hot to cold…..never cold Hot to cold…..never cold to hot!!to hot!!

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

F grav = 4.9NF grav = 4.9N

Net force = 4.9N – 2N = Net force = 4.9N – 2N = 2.9N2.9N

A = F/m 2.9/.5 = 5.8 A = F/m 2.9/.5 = 5.8 m/s/sm/s/s

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

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

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

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

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

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

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

.a. 5.0.a. 5.0b. 0.20b. 0.20 c. 0.12c. 0.12d. 0.083d. 0.083

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

a. 1/60a. 1/60 b. 1/12b. 1/12 c. 1/2c. 1/2 d. 1d. 1 e. 60e. 60

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

f = 1 cycle / (60 f = 1 cycle / (60 s) = (1 / 60) Hzs) = (1 / 60) Hz

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

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

PE to KE or KE to PEPE to KE or KE to PE A bungee cord begins A bungee cord begins

to exert an upward to exert an upward force upon a falling force upon a falling bungee jumper.bungee jumper.

KE to PEKE to PE

PE to KEPE to KE

PE to KEPE 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.

Find Fnet of the Find Fnet of the following:following:

a. 400 N Upa. 400 N Up b. 200N Downb. 200N Down c. 20 N Leftc. 20 N Left

Classify as a transverse Classify as a transverse or compressional waveor compressional wave

SoundSound

UV lightUV light

WaterWater

P wavesP waves

Gamma raysGamma rays

CompressionalCompressional

TransverseTransverse

TransverseTransverse

CompressionalCompressional

TransverseTransverse

Classify as a mechanical Classify as a mechanical or electromagnetic waveor electromagnetic wave

Visible lightVisible light

Earthquake wavesEarthquake waves

SoundSound

Radio WavesRadio Waves

EM WaveEM Wave

MechanicalMechanical

MechanicalMechanical

EM WaveEM Wave

Good Luck!Good Luck!Take your time.Take your time.

See me to ask questions See me to ask questions when you need to.when you need to.

Make me proud!Make me proud!