Transcript Exam Review - Dublin Schools

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
65 N x 4m = 260 Joules
object that weighs
65N and is at a height
of 4m.
35 kg x 9.8 x 40m = 13720 J
 Find the GPE of an
object with a mass of
35 kg and is at a
height of 40m
 1875 Joules
 Find the KE of an object
that has a mass of 6kg
and has a velocity of 25
m/s.
 A forward force of 25 N is put on an
object. It experiences a resistance
force due to friction of 13N.
a. 12 N forward
b. A = F/m
12/.4 = 30 m/s/s
 What is the net force on the object?
 If the object has a mass of 0.4kg,
what rate would it accelerate at?
 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 kick your wall with your foot, your foot hurts!
 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
 Cosmic Background Radiation
 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
 Energy increases
 Frequency increase
 Wavelength decrease
 Speed of light
electromagnetic spectrum
travel at what speed (in a
vacuum)?
 Electromagnetic waves are
transverse/compressional
 Transverse
 If the acceleration of an object
 24 m/s/s
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?
 6 m/s/s
 The acceleration will double
F
H
G
 Name the following parts:
 A
 Wavelength
 D
 Amplitude
 F
 Crest
 G
 Trough
 H
 Equilibrium
Classify the type of heat transfer
 Rubbing your hands together
 Conduction
 Movement of tectonic plates
 Convection
 Warming yourself by a fire
 Radiation
 Movement of air in the
 Convection
atmosphere
 Feet on cold tile floor
 Conduction
HEAT TRANSFER
This type of heat transfer can occur in a
vacuum:
a) Conduction. c) Convection.
b) Radiation. d) Blackbody.

B
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
Heat Transfer
Heat transfer by radiation
a) is not possible from human
beings to their environment.
b) does not occur from light bulbs 
they are too bright.
c) does not require any material
between the radiator and the
object receiving the radiation.
d) 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 45degrees 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. 5.0
b. 0.20 c. 0.12 d. 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. 1/60
b. 1/12
c. 1/2
 d. 1
e. 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.
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.
 KE to PE
 PE to KE
 PE to KE
Find Fnet of the following:
 a. 400 N Up
 b. 200N Down
 c. 20 N Left
Classify as a transverse or
compressional wave
 Sound
 Compressional
 UV light
 Transverse
 Water
 Transverse
 P waves
 Compressional
 Gamma rays
 Transverse
Classify as a mechanical or
electromagnetic wave
 Visible light
 EM Wave
 Earthquake waves
 Mechanical
 Sound
 Mechanical
 Radio Waves
 EM Wave
Good Luck!
Take your time.
See me to ask questions when
you need to.
Make me proud!