Final Exam Flashcards
A point against which position is measured
Reference point
A physical measurement that contains directional information
Vector quantity
A physical measurement that does not contain directional information
Scalar quantity
The time rate of change of an object’s velocity
Acceleration
The motion of an object when it is falling solely under the influence of gravity
Free fall
Why must one use a reference point to determine whether or not an object is in motion?
In order for motion to occur, an object’s position must change. In order to determine position, there must be a reference point. The reference point allows you to determine whether or not position changes.
After a visit to your grandmother’s house, you get in your car to go home. You are in the front passenger’s seat and your mother is driving. As you back out of your grandmother’s driveway, she stands outside, waving good-bye.
a. Who is in motion relative to you?
b. Who is motionless relative to you?
a. Your grandmother is in motion relative to you. Even though your grandmother is standing still, her position relative to you is changing. Thus, she is in motion relative to you.
b. Your mother is motionless relative to you. Her position relative to you does not change. She is therefore motionless with respect to you.
How many miles per hour does a car travel if it makes a 40-mile trip in 30 minutes?
This problem gives us distance and time and asks for speed. We know it is asking for speed because a distance unit divided by a time unit is speed or velocity. There is no direction here, so we are talking about speed. Thus, we need to use Equation (9.1). The problem wants the answer in miles per hour, however. We are given the time in minutes. Thus, we must make a conversion first:
What is the velocity of a bicycle (in meters per second) if it travels 1 kilometer west in 4.1 minutes?
The problem wants velocity, which is speed and direction. To get speed, we will use Equation (9.1). Unfortunately, the problem tells us to give the answer in meters per second, but the distance is in kilometers and the time is in minutes. Thus, we need to do two conversions:
You are looking in a scientist’s lab notebook and find the following unlabeled measurements. In each case, determine what physical quantity the scientist was measuring.
a. 12.1 meters per second
b. 31.2 feet
c. 14 millimeters per hour to the west
d. 4.5 yards per minute2 north
a. This measurement has a distance unit divided by a time unit. That’s speed or velocity. Since no direction is given, this is speed.
b. The unit of feet by itself measures distance.
c. This measurement has a distance unit divided by a time unit. That’s speed or velocity. Since a direction is given, this is velocity.
d. This measurement has a distance unit divided by a time unit squared. That’s acceleration. The direction is necessary because acceleration is a vector quantity.
An eagle swoops down to catch a baby rabbit. Luckily for the rabbit, he sees the eagle and runs. An all-out chase ensues with the rabbit running east at 5.4 meters per second and the eagle pursuing at 4.4 meters per second. What is the relative velocity of predator and prey?
As the picture shows, the eagle is behind the rabbit, but they are both traveling in the same direction. Thus, we get their relative velocity by subtracting their individual velocities:
relative velocity = 5.4 meters/second - 4.4 meters/second = 1.0 meter/second
Since the rabbit is traveling faster than the eagle, the rabbit is pulling away. Thus, the relative velocity is 1.0 meter per second away from each other.
What is the acceleration of an object that moves with a constant velocity?
Since the velocity is not changing, the acceleration is zero.
A skier reaches the bottom of a slope with a velocity of 12 meters per second north. If the skier comes to a complete stop in 3 seconds, what was her acceleration?
The initial velocity is 12 meters per second north, and the final velocity is 0. The time is 3 seconds. This is a straightforward application of Equation (9.2).
A car goes from 0 to 60 miles per hour north in 5 seconds. What is the car’s acceleration?
This is another application of Equation (9.2), because we are given time (5 seconds), initial velocity (0) and final velocity (60 miles per hour north). We can’t use the equation yet, however, because our time units do not agree. We’ll fix that first:
A person standing on a bridge over a river holds a rock and a ball in each hand. He throws the ball down towards the river as hard as he can and at the same time simply drops the rock. After both have left the person’s hand, does one have a greater acceleration? If so, which one?
Neither has greater acceleration. Both objects are falling near the surface of the earth; thus, they are each in free fall. That means they both have equal acceleration. The ball was given moreinitial velocity, so it will travel faster. The acceleration on both is the same, however.
Why does a dropped feather hit the ground later than a rock dropped at the same time?
The feather is more affected by air resistance than the rock. This is the same situation as Experiment 9.2.
A physics student climbs a tree. To measure how high she has climbed, she drops a rock and times its fall. It takes 1.3 seconds for the rock to hit the ground. How many feet has she climbed?
The rock is in free fall, so we can use Equation (9.3). Since the problem wants the answer in feet, we need to use 32 feet per second2 as the acceleration.
The tendency of an object to resist changes in its velocity
Inertia
A force that opposes motion, resulting from the contact of two surfaces
Friction
Friction that opposes motion once the motion has already started
Kinetic friction
Friction that opposes the initiation of motion
Static friction
State Newton’s three laws of motion.
Newton’s First Law – An object in motion (or at rest) will tend to stay in motion (or at rest) until it is acted upon by an outside force.
Newton’s Second Law – When an object is acted on by one or more outside forces, the total force is equal to the mass of the object times the resulting acceleration
Newton’s Third Law – For every action, there is an equal and opposite reaction.
A pilot is flying a mission to drop bombs on an enemy airfield. The plane is flying high and fast to the north, and the city is due north. Should the pilot drop the bombs before the plane is over the airfield, when the plane is over the airfield, or after the plane has passed the airfield?
The pilot must drop the bombs before the plane reaches the airfield. The bombs will have a velocity equal to that of the plane when they are dropped. Thus, they will continue to fly north as they fall. In order to hit the airfield, then, they must be dropped south of it.
A cruel boy has placed a mouse on the outer edge of a disk. He slowly starts to spin the disk, accelerating it faster and faster until the disk and mouse are both spinning around at an alarming rate. What will happen to the mouse if the boy suddenly stops the disk without touching the mouse: will the mouse continue to spin like it was before; will the mouse stop with the disk; or will the mouse start moving straight, skidding off the disk?
The mouse will start moving straight, skidding off of the disk. This is like Experiment 10.2. When the disk stops, the mouse has a velocity pointed in a certain direction. Without sufficient time, the frictional force will not be able to keep the mouse on the disk. This will cause the mouse to start traveling in a straight line, in the direction it was moving right before the disk stopped.
An ice cube (mass = 1.0 kg) slides down an inclined serving tray with an acceleration of 4.0 meters per second2. Ignoring friction, how much force is pulling the ice cube down the serving tray?
Since we are ignoring friction, this is an easy problem:
A baseball player (mass = 75 kilograms) is running north towards a base. In order to avoid being tagged by the ball, the baseball player slides into the base. If his acceleration in the slide is 5.0 meters per second2 south, what is the kinetic frictional force between the baseball player and the ground?
The baseball player is slowing, because his velocity is north but the acceleration is directed south. Friction slows things down. This is the only force in the problem, since nothing else is pulling or pushing on the player. Thus, the force that results from the acceleration will be the frictional force.
A man pushes a heavy cart. If the man exerts a force of 200 Newtons on the cart to keep it moving at a constant velocity, what is the frictional force between the cart and the ground? Is this kinetic friction or static friction?
If the cart is moving with a constant velocity, that means the acceleration (and thus the total force) equals zero. Thus, the man must be pushing with just enough force to counteract friction. Thus, the frictional force is 200 Newtons against the motion of the cart. This is kinetic friction, because the cart is moving.
You are looking through a physicist’s laboratory notebook and notice two numbers for the friction between a block of wood and a laboratory bench. The numbers are 8 Newtons and 11 Newtons. Which refers to static friction and which refers to kinetic friction?
Since static friction is generally greater than kinetic friction, 11 Newtons refers to static friction, and 8 Newtons refers to kinetic friction.
A woman pushes a box (mass = 30 kilograms). The static friction between the box and the ground is 20 Newtons, while the kinetic friction is 7 Newtons. How much force must the woman exert to get the box moving? With what force must she push the box in order to get it to accelerate at 1.0 meters per second2 to the west?
If the static frictional force is 20 Newtons, the woman must overcome it to get the box moving. To get the box moving, then, a force greater than 20 Newtons must be used. Once the box is moving, the acceleration is 1.0 meters per second2, so the total force is:
When baseball players hit the ball hard enough, their bats can sometimes break. What is exerting a force on the bat, causing it to break?
The ball exerts a force on the bat. This is the equal and opposite force demanded by Newton’s Third Law.
What theory says that gravity is caused by the exchange of particles between objects with mass?
The Graviton Theory
A child is twirling a toy airplane on a string at a constant speed:
Which arrow represents the force the plane is experiencing?
Arrow A
The weakest of the fundamental forces is gravity.
True
The gravitational force between two objects (mass1 = 5 kg, mass2 = 2 kg) is measured when the objects are 10 centimeters apart. If the 5 kg mass is replaced with a 20 kg mass and the 2 kg mass is replaced with a 12 kg mass, how does the new gravitational attraction compare to the first one that was measured?
The new gravitational force is 24 times larger than the old one.
Use the following diagram to answer the question.
Which of the orbits is more likely that of a comet?
orbit c
The gravitational force between two objects (mass1 = 10 kg, mass2 = 6 kg) is measured when the objects are 12 centimeters apart. If the distance between them is increased to 36 centimeters, how does the new gravitational attraction compare to the first one that was measured?
The new gravitational force is 9 times smaller than the old one.
Suppose a scientist determines that there are only two fundamental forces in nature: the electroweak force and the strong force. Which of the two current theories of gravity does this mean is true?
The Graviton Theory would be true in this case.
A child is twirling a toy airplane on a string at a constant speed:
Which arrow represents the velocity of the plane?
Arrow C
A child is twirling a toy airplane on a string at a constant speed:
What kind of force is the plane experiencing (as shown by one of the arrows)?
Centripetal force
Two moons orbit different planets, but they orbit their planets at the same distance. If the first one takes 3 months to make an orbit and the second takes 1 year, which is being subjected to the greatest gravitational attraction?
The first moon experiences the greatest gravitational force.
Jupiter is the planet in the solar system that receives the least amount of insolation.
False
A student drops a ball, and it begins to fall due to the force of gravity that the earth exerts on it. What is the equal and opposite force demanded by Newton’s Third Law of Motion?
The equal and opposite force is the earth’s gravity, or if you were talking about the ball, it would be the ball’s mass.
The Kuiper belt is a source of long-term comets.
False
What part or parts of a comet come and go during a comet’s orbit?
The coma and tail come and go, depending on the proximity to the sun.
The outer planets are Mars, Jupiter, Saturn, Neptune, Pluto.
False
The force between the south pole of one magnet and the south pole of another magnet is measured. The distance between those magnets is suddenly doubled.
How will the new force compare with the old one?
The new force decreases by a factor of four.
The force between the south pole of one magnet and the south pole of another magnet is measured. The distance between those magnets is suddenly doubled.
Repulsive
You cut a magnet in half - right between the north and south poles. How many north poles and south poles do you now have?
You will have two north poles and two south poles.
A physicist charges an object with a positively-charged rod. If the object develops a negative charge, how did the physicist charge the object?
The object developed a charge opposite of the rod. Thus, the object was charged by induction.
A measure of how much a metal impedes the flow of electrons.
Resistance
Small “packages” of light that act just like small particles.
Photons
A circuit that does not have a complete connection between the two sides of the battery. As a result, current does not flow.
Open circuit
Charging an object by forcing some of the charges to leave the object.
Charging by induction
Charging an object by allowing it to come into contact with an object which already has an electrical charge.
Charging by conduction
Current that flows from the positive side of the battery to the negative side. This is the way current is drawn in circuit diagrams, even though it is wrong.
Conventional current
The amount of charge that travels through an electrical circuit each second.
Electrical current
The atoms in an object are not aligned. Is the object a magnet? Why or why not?
No. A magnet must have their atoms aligned in order for it to be considered a magnet.
In most chandeliers today, when one light bulb goes out, the rest stay lit. Are the light bulbs wired in series or in parallel?
The light bulbs are wired in parallel.
Will the objects shown bellow attract or repel each other?
The two objects have opposite charges, so they will attract each other.
Look at the circuit diagram below:
Which arrow represents the conventional current flow?
The dashed line and arrows.
You are blindfolded and handed two extension cords. Both have the same current running through them. If the cord in your left hand is warmer than the one in your right hand, which cord is thicker?
The cord in your right hand.
If a circuit has a low voltage, is there any way to get a lot of energy from it? If so, how?
A low voltage means that each electron will have only a little bit of energy. You can still get a lot of energy out of the circuit, however, as long as you put a lot of current through it.
Look at the circuit diagram below:
Which arrow represents the flow of electrons?
The solid line and arrows.
The center of an atom, containing the protons and neutrons
Nucleus
The number of protons in an atom
Atomic number
The sum of the numbers of neutrons and protons in the nucleus of an atom
Mass number
Atoms with the same number of protons but different numbers of neutrons
Isotopes
A collection of atoms that all have the same number of protons
Element
An atom with a nucleus that is not stable
Radioactive isotope
Which is larger, an electron or a proton? Which is negatively charged?
A proton is larger than an electron. An electron is negatively charged.
What causes the nuclear force, and why can this force act only over very short distances?
The nuclear force is caused by the exchange of pions. It is a short-range force because pions can only exist for a short time.
List the number of protons, neutrons, and electrons in the following atoms:
a. 48Ca
b. 124Sn
c. 109Ag
a. Since the chemical symbol is Ca, we can use the chart to learn that the atom has 20 protons. This tells us there are also 20 electrons. The mass number is the sum of protons and neutrons in the nucleus. Thus, there are 28 neutrons.
b. Since the chemical symbol is Sn, we can use the chart to learn that the atom has 50 protons. This tells us there are also 50 electrons. The mass number is the sum or protons and neutrons in the nucleus. Thus, there are 74 neutrons.
c. Since the chemical symbol is Ag, we can use the chart to learn that the atom has 47 protons. This tells us there are also 47 electrons. The mass number is the sum of protons and neutrons in the nucleus. Thus, there are 62 neutrons.
Draw an illustration of what the Bohr model says a 23Na atom looks like.
All atoms symbolized with “Na” have 11 protons according to the chart. This also means there are 11 electrons. Two of them can go into the first Bohr orbit, and 8 can go in the second Bohr orbit. We will have to put the remaining one in the third Bohr orbit. The mass number indicates that there are 12 neutrons:
Which of the following atoms are isotopes?
144Ce, 144Nd, 144Sm, 145Nd
Isotopes have the same number of protons but different numbers of neutrons. Since chemical symbols tell us the number of protons, we are looking for atoms with the same chemical symbol but different mass numbers. Thus, 1<span>44</span>Nd and 145Nd are isotopes.
A radioactive isotope has a half-life of 3 hours. If a scientist has 30 grams of the isotope, how much is left after 15 hours?
In the first three hours, the 30 gram sample will be reduced to 15 grams. In the next three hours, it will be reduced to 7.5 grams. In the next 3 hours, it will be reduced to 3.75 grams. In the next three hours, it will be reduced to 1.875 grams. In the next 3 hours, it will be reduced to 0.9375 grams.
What is the daughter product in the beta decay of 144Ce?
144Ce has 58 protons according to the chart. This means there must be 86 neutrons. In beta decay, a neutron turns into a proton. This will result in an atom with 59 protons and 85 neutrons, or 144Pr.
What is the daughter product in the alpha decay of 220Rn?
220Rn has 86 protons according to the chart. This means there must 134 neutrons. In alpha decay, the nucleus loses 2 protons and 2 neutrons. This will result in an atom with 84 protons and 132 neutrons, or 216Po.
What is the daughter product in the gamma decay of 239U?
In gamma decay, the number of protons and neutrons is unaffected by the decay. Thus, the daughter product is the same as the original 239U.
If a piece of paper is placed between a radioactive isotope and a person, which kind of radioactive particle will the person be protected from?
The person would only be protected from alpha particles.
Which waves have the longest wavelength?
Infrasonic waves
An amplifier at a concert takes a 30 decibel sound and turns it into an 80 decibel sound.
Is the amplified sound loud enough to damage a person’s eardrum?
No, 80 decibels is within a normal person’s hearing threshold.
A jet travels through 10˚C air at Mach 3. What is its speed in meters per second? (Show your work.)
(331. 5 + 0.6 • 10) m/sec
337. 5 m/sec • 3
1012.5 m/sec
During a thunderstorm, the temperature is 10˚C. If you see a lightning strike and then hear the thunder 2 seconds later, how far away did the lightning strike?
675 m
What is the speed of sound in air that has a temperature of 25˚C?
346.5 m/sec
A man and woman are singing a duet. The man sings the low notes and the woman sings the high notes. The woman, since she is singing the melody, is louder than the man.
How do the wavelengths of the man’s sound waves compare to those of the woman?
The man’s sound waves have longer wavelengths than the woman’s.
A sound wave traveling through 17˚C air has a wavelength of 2 meters. What is the frequency of the sound wave? (Show your work.)
(331. 5 + 0.6 • 17) m/sec
341. 7 m/sec/ 2m
170.85 1/sec
An amplifier at a concert takes a 30 decibel sound and turns it into an 80 decibel sound.
How many times larger is the intensity of the sound waves coming out of the amplifier as compared to the intensity of the sound waves going into the amplifier?
The sound wave intensity is 100,000 times larger.
A ship blows its horn. Some of the sound waves travel through the air and then hit the water. Will the sound waves travel faster in the water or in the air?
The sound waves will travel faster in the water.
A popular science fiction movie was advertised with the slogan, “In space, no one can hear you scream.” Is this a true statement? Why or why not?
Yes. Since there is no air in space, our voices, or any sound, cannot be heard because the sound waves are blocked.
Do sound waves oscillate parallel to or perpendicular to the direction in which the wave travels?
Parallel
You are driving in a city that has a siren which sounds for 30 seconds every day at noon. You stop at a stoplight and then hear the sound of the siren. The stoplight then turns green, and you start driving. As you speed up, you notice that the pitch of the siren keeps getting higher. Are you driving towards or away from the siren? (Assume that the true pitch of the siren stays constant.)
You are driving towards the siren.
The highness or lowness of a sound.
Pitch
The lowest point in a wave.
Trough
A wave whose propagation is parallel to its oscillation.
Longitudinal wave
The highest point in a wave.
Crest
Any speed that is faster than the speed of sound in the substance of interest.
Supersonic speed
The sound produced as a result of aircraft traveling at or above Mach 1.
Sonic boom
A wave whose propagation is perpendicular to its oscillation.
Transverse wave
A man and woman are singing a duet. The man sings the low notes and the woman sings the high notes. The woman, since she is singing the melody, is louder than the man.
How do the speed of the sound waves compare?
The man’s sound waves have the same speed as the woman’s.
A man and woman are singing a duet. The man sings the low notes and the woman sings the high notes. The woman, since she is singing the melody, is louder than the man.
How do the amplitudes of the waves compare?
The man’s sound waves have smaller amplitude than the woman’s.
A man and woman are singing a duet. The man sings the low notes and the woman sings the high notes. The woman, since she is singing the melody, is louder than the man.
How do the frequency of the man’s sound waves compare to those of the woman?
The man’s sound waves have lower frequencies than the woman’s.
A recorder is a woodwind instrument in which the player blows into a tube, setting up a wave in the tube. A musician has 2 recorders. The first one is rather short, and the second one is significantly longer. Which recorder is capable of playing notes with the lowest pitch?
The long recorder.
What does the eye do to change its focus?
To change its focus, the eye changes the shape of the lens.
You are on a diving board looking down into a pool. You see a quarter at the bottom of the pool, about three feet in front of you. Why is the quarter really not 3 feet in front of you? Where is it?
Water refracts light, making objects appear at a different place. The quarter is closer to you.
The angle of reflection equals the angle of incidence.
The Law of Reflection
The subtractive primary colors.
Magenta, yellow, and cyan
The light which we see with our eyes.
Visible spectrum
A representation of all the light in Creation.
Electromagnetic spectrum
A transverse wave composed of an oscillating electrical field and a magnetic field that oscillates perpendicular to the electrical field.
Electromagnetic wave
The additive primary colors.
Red, green, and blue
Which has the highest frequency?
blue light
For the next few questions, remember that blue + green = cyan, red + blue = magenta, and red + green = yellow.
If cyan and magenta ink is mixed, what color ink will you get?
ou will get blue ink.
Which has longest wavelength?
radio waves
The speed of light in glass is 185,000,000 m/sec. If a particle is traveling through air at 200,000,000 m/sec, what has to happen to the particle’s speed if it enters the glass?
It will slow down.
Describe light according to the currently accepted theory. Be very detailed.
According to the accepted theory, light is both a particle and a wave. It looks like it is made up of particles, but it acts like a wave. There are individual packets of light in a wave-like sequence.
You want to concentrate light coming from a weak light source by focusing it all on a single point. Would you use a converging or diverging lens to do this?
A converging lens
Which picture shows what happens to the light ray when it hits the right side of the aquarium?
Picture d
For the next few questions, remember that blue + green = cyan, red + blue = magenta, and red + green = yellow.
If a computer monitor makes a green dot and then puts a blue dot in the same place, what color will you see?
You will see a cyan dot.
For the next few questions, remember that blue + green = cyan, red + blue = magenta, and red + green = yellow.
If you shine red light on a yellow shirt, what color will the shirt appear?
It will appear red.
The process by which two or more small nuclei fuse to make a bigger nucleus
Nuclear fusion
The process by which a large nucleus is split into smaller nuclei
Nuclear fission
The amount of isotope necessary to sustain a chain reaction
Critical mass
The brightness of a star, corrected for distance, on a scale of -8 to +19. The smaller the number, the brighter the star.
Absolute magnitude
The brightness of a star as seen in the night sky. The smaller the number, the brighter the star.
Apparent magnitude
The distance light could travel along a straight line in one year
Light year
A large ensemble of stars, all interacting through the gravitational force and orbiting around a common center
Galaxy
What nuclear process occurs in the sun’s core?
Nuclear fusion occurs in the sun’s core.
A 4He nucleus and a 7Li nucleus collide and form a 10B nucleus and a neutron. Is this nuclear fusion or nuclear fission?
This is nuclear fusion, since two small nuclei fused to make a bigger one.
A scientist studies a process in which a neutron strikes a 216Pu nucleus to make a 104Cd nucleus, a 110Pd nucleus, and three neutrons. If the scientist measures the mass of the 216Pu and the original neutron and then subtracts the mass of the 104Cd nucleus, the mass of the 110Pd nucleus, and the mass of the three neutrons, will the scientist get a positive number, a negative number, or zero?
He would get a positive number. In nuclear fission and fusion, mass is converted into energy. Thus, the mass of the materials produced will be less than the mass of the starting materials.
Is it possible for a nuclear power plant to experience a nuclear explosion? Why or why not?
It is not possible, because a power plant does not have significantly more than the critical mass of the large nucleus.
Using the H-R diagram below, classify the following stars:
a. Magnitude 5, Spectral Letter G
b. Magnitude 2, Spectral Letter K
c. Magnitude 11, Spectral Letter B
d. Magnitude -6, Spectral Letter A
Using the magnitudes and spectral letters given, we have:
This tells us the classifications are:
a. Main sequence
b. Red giant
c. White dwarf
d. Supergiant
Which is the brightest of the stars in problem #6?
The brightest star is the one with the lowest magnitude. Thus, (d) is the brightest star.
Which is the hottest of the stars in problem #6?
The hottest star is the one that is the farthest to the left on the H-R diagram, because temperature increases the farther left you travel on the H-R diagram. Thus, (c) is the hottest star.
What are the two main types of variable stars?
The two main types of variable stars are novas and pulsating variables.
What are Cepheid variables, and why are they important in astronomy?
Cepheid variables are variable stars whose magnitude and period have a direct relationship. They are important in astronomy because that relationship can be used to measure long distances in the universe.
What is the name of the galaxy to which earth’s solar system belongs? What type of galaxy is it?
Earth’s solar system belongs to the Milky Way galaxy, which is a spiral galaxy.
What is the red shift?
The red shift is the phenomenon in which light that comes to the earth from other galaxies ends up having longer wavelengths than it should. Most astronomers interpret that as a Doppler shift resulting from the expansion of the universe.
