Quiz hints (a.k.a. Study questions) for Physics P100

Don't forget, Quizzes also  include:

Questions  about the lab exercises.

Questions you missed on the last quiz.

Questions on homework assignments.

Questions similar to the ones we did in class.

Science and units:

Explain in your own words the 'scientific attitude'.

What is the difference between science and pseudo science? Give some examples.

Why do we think astronomy is a correct way of viewing the universe but astrology is not?

What is the difference between science and religion? Do the two conflict with each other or not? Explain.

What is the difference between science and technology? Scientists are responsible for science, who is responsible for technology?

Why are approximations useful in physics? (Aren't scientists always interested in exact answers?)

If x and y represent physical quantities which have different units, which of the following operations are possible? a) x+y b) x-y c) xy d) x/y e) y/x

If r is measured in m/s , s is measured in J = kg m²/s², k in kg, L in m and p in s, which of the following equations at least could be true based on their units? a) Lp² = s; b) L/p = r c) r² k = s; d) pk³ = s/L; e) 1/r = p/L

Newton's first law:

If the total force (sum of all forces acting in each direction) is zero on an object can it have a non zero velocity ? Give an example.

According to Newton's second law, F = ma. Give an example where the forces on an object are not zero but the acceleration is zero.

A car is traveling at a constant 60 mph. What is the net force acting on the car ?

A marble sinks through a jar of honey at constant velocity. What can you say about the friction force on the marble?

A marble was stuck to a rotating turntable but suddenly comes loose. Where does the force come from that pushes the marble off the turntable?

Whiplash results from an automobile accident in which the victim's car is struck violently from the rear. Explain why the head of the victim seems to be thrown backward in this situation. Is it really ?

Since the earth is turning at a great speed, why is it that if you jump up in the air you are not instantly slammed against the wall?

You are going to use a pulley and a single rope to support a weight hung from the ceiling. There are two was to do this: 1) you and tie one end of the rope to the ceiling, string the rope through the pulley, attach the pulley to the object and then pull up on the rope or 2) you can attach the pulley to the ceiling and the rope to the object , run the rope through the pulley and pull down on the pulley. Which way is easier and why?

Linear motion and the acceleration of gravity:

Does a car speedometer measure speed or velocity? What is the difference?

What is the difference between velocity and acceleration?

If an object has an instantaneous velocity of zero, can it have a non zero acceleration? Give an example.

Can a rapidly moving object have the same acceleration as a slowly moving one? Explain.

A ball is thrown up into the air. What is its acceleration on the way up? On the way down? At the very top when it stops to turn around?

If the acceleration is the same on the way up, the way down and the very top of the path of a ball thrown up into the air, how do the velocities compare at these points?

At the end of its arc, the velocity of a pendulum is zero. Is its acceleration also zero at this point? Why or why not?

Which takes longer to reach the ground; a ball dropped from the window of a moving car or one dropped from the same height of a stationary car? Explain.

Draw a graph of a constant velocity line. What is the value of the velocity of the line you have drawn?

Sketch a graph of the motion of an object with zero acceleration on a velocity versus time graph. (velocity vertical, time horizontal)

What physical quantity is represented by the slope of a distance versus time graph?

What physical quantity is represented by the slope of a velocity versus time graph?

Newton's second law of motion:

Explain the difference between mass and weight.

You are in space where objects appear to be weightless. Which is harder to accelerate, a baseball or a refrigerator (or does it make any difference since they are weightless)?

If the acceleration of an object is zero, does it mean there are no forces acting on it or no net force? Explain the difference.

Without air resistance a heavy skydiver would accelerate at the same rate that a light skydiver would so at any instant they would have the same speed. With air resistance, however, the heavy skydiver ends up with a higher thermal velocity than the light skydiver. Explain how this happens.

If you lock the wheels on your car while coming to a stop and utilize kinetic rather than static friction, does your stopping distance increase or decrease? Explain.

A big car and a small car collide. From Newton's third law we know the two cars will experience the same force. Which car experiences the bigger acceleration?

Newton's third law of motion:

A dropped rubber ball will bounce. Which of Newton's three laws explains where the force comes from which causes the ball to bounce back into the air?

Why does a runner accelerate if Newton's third law is correct ? Isn't the net force zero in this case ? How can anything move if there are always two forces which are equal and opposite?

A car going down the highway hits an smashes a bug. Which has the larger force on it, the bug or the car? (Careful!)

If you hop off of a chair the earth's gravity pulls you down. Name the reaction force and what it acts on in this case.

Momentum:

If you were to fall out of a third floor window, which would you rather land on, concrete or a hay stack? Explain why.

If you throw and egg at a wall it will break but if you throw it at a sheet held up loosely by two people it does not. Why?

How can a rocket work in space where there is nothing for the exhaust to push against?

What is the difference between an elastic collision and an inelastic collision?

Under what cases can you apply momentum conservation?

Is momentum conserved when a ball of putty hits the floor?  Explain.

Momentum and kinetic energy both have mass and velocity in them. What, then, is the difference between conservation of momentum and conservation of energy?

A big car and a small car collide and stick together. You now know that the force on each is the same but the acceleration of the small car is more than the acceleration of the big car. Which car has the biggest momentum change?

An empty box slides across the frictionless surface of a frozen lake.  Which principle of physics tells you that the box will slow down as water collects in it from a rain shower?

Which principle of physics tells you that a rifle will recoil when a bullet is fired from it?  (the answer is not Newton's third law)

A ball dropped onto a hard surface will rebound.  The momentum of the ball is clearly not conserved since it's change in momentum is 2mv if it rebounds with the same velocity.  Does this contradict the law of conservation of momentum?  Explain.

Why does an inflated balloon fly across the room when released?  (The answer is not Newton's third law.)

Conservation of energy:

Can gravitational potential energy be negative? Explain.

Can kinetic energy be negative? Explain.

A dog is pulling on his chain the other end of which is attached to a tree. Is the dog doing any work?  Explain.

Why is it easier to climb a mountain via a zigzag trail rather than climbing straight up?

When a baseball is being thrown, is any work done on the ball while it is in contact with the pitchers hand? Explain.

When a baseball is being thrown, is any work done on the ball after it has left the pitchers hand? Explain.

We know the net force on a car moving at constant velocity is zero. We also know work is done by the motor. How can this be?

What is efficiency?

Gasoline engines are only about 30% efficient at best. Where does the rest of the energy go?

Is it possible to build an engine or other device that puts out more energy than it consumes? Why not?

Which of the following are always conserved? momentum, kinetic energy, total energy, work, potential energy

Which of the following are conserved in an inelastic collision? momentum, kinetic energy, total energy, work, potential energy

There is a book on your table. To measure its gravitational potential energy does it matter if you measure h from the floor of the room below us?

What is the ultimate source of the energy found in fossil fuels?

What is the difference between power and energy?

Rotation:

It is possible to tell a hard boiled egg from a fresh egg by spinning it. Explain why the hard boiled egg spins but the the raw one will not.

What is the difference between rotational inertia and angular momentum?

Which would be easier to stop, a rotating bicycle tire filled with air or one filled with water? Explain.

What is torque?

During the spin dry cycle of a washing machine water leaves clothes as they spin at a high speed. What is the direction of the force acting on the clothes? What applies this force?

During the spin dry cycle of a washing machine water leaves clothes as they spin at a high speed.  The washing machine contains holes large enough to let water out but too small to allow the clothes out.  Explain why the water separates from the clothes.

Why does a spinning top not turn over?

Draw a diagram of an object traveling in a circle and show the relative directions of centripetal force, centripetal acceleration, and tangential acceleration.

Why does a football which spins on its axis not tumble after it is thrown?

Communication satellites have antennae that must always point in the same direction.  This can be accomplished by causing the satellite to spin. Why does this help and what principle in physics is used here?

Why is it easier to loosen a bolt if you hold the end of the wrench rather than the middle?

Explain how a child on a swing can cause the swing to rise higher and higher with out touching the ground by pumping his feet back and forth.

During the spin dry cycle of a washing machine water leaves clothes as they spin at a high speed.  The washing machine contains holes large enough to let water out but too small to allow the clothes out.  Explain why the water separates from the clothes.

Projectile motion and vectors:

A tennis ball traveling at 1m/s rolls off the edge of a horizontal table top. List the following at the instant it leaves the table: 1) y velocity, 2) x velocity, 3) x acceleration , 4) y acceleration.

A hunter aims a gun directly at a monkey hanging from a limb. He points the gun directly at the monkey, failing to take into account gravity acting on the bullet. The monkey lets go and falls at the exact instant the bullet is fired. Will the monkey get hit or not ? Explain.

Why do we need vectors in physics?

What are Kepler's laws?

Why are Newton's laws some how 'better' than Kepler's laws?

What is a geo-sychronus orbit?

Solids and liquids

• What is the difference between an atom and a molecule?
• What are atoms made of?
• Why do we use Avagadro's number when talking about atoms?
• What do we mean when we say matter is mostly "empty space"?
• How are copper atoms different from Oxygen atoms?
• What is the difference between density and mass?
• What happens to the volume of a marshmallow that gets squished? The mass? The density?
• What is Brownian motion and what does it tell us about atoms?
• What are the four phases of matter?
• Explain why a battleship floats even though it is made of iron which is more dense than water.
• A siphon is a tube which transfers liquid from a higher level to a lower level.  How does it work?
• Explain how a straw works.
• Lead and iron are both denser than water. If a block of the same size of each is submerged in water, which will have the greater buoyant force? Explain.
• Fish have swim bladders which alter the volume of the fish. What effect does this have on the fish? Explain.
• Will a boat float higher or lower in fresh water as opposed to salt water? Explain.
• A person in a boat floating in a small pond throws a heavy anchor over board.  Does the level of the pond rise, fall or remain the same?
• Why does a sharp knife cut better than a dull knife (even when you apply the same force)?
• A friend wants to use a piece of garden hose with one end above water to go to the bottom of a pool 3m deep. What advice should you give them?

Heat and heat transfer

• If a city is hotter than the surrounding countryside, why do you expect breezes to flow into the city from the surrounding countryside?
• Concrete has a higher specific heat than does soil.  Use this fact to argue that cities have a higher average temperature than the surrounding countryside.
• A baking potato has a specific heat capacity of 1.2 cal/g^oC.  A slice of hot apple pie with the same mass has a heat capacity of 0.8 cal/g^oC.  If they both start with the same temperature and are in the same environment, which will  cool faster and why?
• What is the difference between heat and temperature?
• A bimetallic strip is made of two pieces of metal joined along their length.  The metals are chosen with different coefficients of expansion so that the strip bends as it is heated.  Describe how you would calibrate this device in order to  make a thermometer.
• Tell me every thing you know about absolute zero.
• Why do most things expand when heated?
• Water has an important property that makes it different from most substances when it is heated from zero to 4 Celsius. Explain.
• When a circular metal ring is heated from 20C to 50C does the hole get smaller of larger?
• Explain the four means of heat transfer.
• If you add heat to a substance, does the temperature always rise?  Explain.
• Why would you expect the temperature of a jar of water to increase when shaken vigorously?
• How does a thermos bottle keep a cold liquid inside cold?
• How does a thermos bottle keep a hot liquid inside hot?
• Why does metal feel cool to the touch but wood feels warm, even when they are at the same temperature?
• When you add heat to boiling water the temperature does not go up until the water is gone. Why is that?
• From a molecular point of view, how does evaporative cooling work?

Thermodynamics

Explain the first law of thermodynamics.

Explain the second law of thermodynamics.

Why can't you make a car that is 100% efficient?

Why can you heat a room by opening the stove and turning it on but you can't cool a room by opening the refrigerator and leaving it on?

What happens to the efficiency of a heat engine if the temperature of the cool reservoir is increased? Explain.

Do organisms break the second law of thermodynamics when the grow up to become more ordered? Explain.

Waves and vibrations

What is the difference between longitudinal and transverse waves?

Explain the superposition principle for waves.

Pitch in a sound wave corresponds to which numerical quantity?

What quality does frequency tell you about for visible light?

How are wavelength and frequency related?

What is interference of waves? Give some examples.

What is the Doppler effect? Give some examples of the use of the Doppler effect in every day life.

What are sound waves?

Why don't sound waves travel in a vacuum?

Do radio waves travel in a vacuum? Light waves?

If you hear the sound of thunder 3s after you see the lightening, about how far away is the storm?

What is resonance?

What are beats?

How is an AM signal different from FM?

What is the difference between radio waves and sound waves?

Electrostatics

Conservation of charge is our 4th conservation law this semester. how is it different from the other three conservation laws we have studied?

It is possible to demonstrate the electrical attraction between two charged objects very easily as was shown in class.  Why is it much more difficult to demonstrate the gravitational attraction between two small objects?

If the electrical force is so much stronger than the gravitational force, why does gravity and not electrical force hold the moon in orbit around the earth?

Would it make any difference if all of the electrons in the world suddenly became positive if, at exactly the same time all the protons in the world became negative? Why?

What is the difference between an insulator, a conductor, a super conductor and a semiconductor?

What is an electric field and why do we need it in this chapter?

An electric field points north. Which direction is the force on an electron in this field? How about a proton?

What is the difference between electric field and electric potential?

What is the difference between electric potential energy and electric potential?

What is a capacitor?

Electric current

What are the units of electrical resistance?

How much current is dangerous to humans? (See table 22.1)

What is the difference between AC and DC?

Name some items in you house that are or should be connected in parallel.

Name some items in you house that are or should be connected in series.

How does a fuse or circuit breaker work? Is it in series or parallel with the device it is protecting?

Watt is the units of electrical power?

What is the difference between  volts and amperes?

What is the difference between current and voltage?

Name some items in you house that are or should be connected in parallel.

Name some items in you house that are or should be connected in series.

How does a fuse or circuit breaker work? Is it in series or parallel with the device it is protecting?

Magnetism

How are magnetic poles similar to electric charges and how are they different?

What is a magnetic domain?

What causes magnetic fields?

How does the earth's magnetic field protect us from charged particles coming from the sun?

What are the Van Allen radiation belts and how did they form?

Why do the aurora (aurora borealis in the north, aurora austrailis in the south) form only at the earths magnetic poles?

Explain how an unmagnetized piece of iron is attracted to both the north and south poles of a magnet.

How does an electric motor work?

What effect does a magnetic field have on an electric charge?

How can you make a magnet?

How can you make an electromagnet?

A piece of iron which originally unmagnetized is heated while oriented in a north-south direction.  When it is cooled it is found to have a permanent magnetic field.  Explain what happened.

Electromagnetic induction

What is electromagnetic induction?

Explain how a generator works.

Why don't transformers work with direct current?

Why is power transmitted at high voltages (and low current) over long distances?

What is Faraday's law?

 Credit cards, traffic sensors, cassette tapes and generators all use Faraday's law. How does each work?

A transformer with 10 turns in the primary and 100 turns in the secondary will convert an AC voltage of 5 V to 50 V.  Explain why this doesn't contradict conservation of energy?

Light, color, reflection, refraction, light waves

• How do you make an electromagnetic wave?
• Under what circumstances do we expect to see the effects of diffraction?
• What is the difference between diffraction and interference?
• Under what circumstances do we expect to see the effects of diffraction?
• What is the difference between diffraction and interference?
• Radio waves diffract around buildings, whereas light, which is also electromagnetic, does not. Why?
• Explain how you would make a coating for a binocular lens that was non-reflective for a particular frequency.
• Why do soap bubbles show different colors?
• Why do oil slicks show different colors?
• Some insect wings have pretty colors which change when viewed at different angles. How does this work?
• Can sound waves be polarized? Why or why not?
• In the demonstration using the laser light in class, why did the beam go straight through the door yet bend into a diffraction pattern when passing through a slit cut into a piece of plastic?
• Why is the sky blue and sunsets red?

Light emission and light quanta

• Why is the sky blue and sunsets red?
• How can you tell the temperature of a hot glowing object?
• What is the difference between incandescence (black body radiation) and emission spectra?
• What practical purpose has been made (by chemists) of the fact that different elements give off unique emission spectra?
• Do all objects at any temperature give off black body radiation?
• What is the particle nature of light called?
• Why does ultraviolet light cause tanning and skin cancer but even very bright visible light does not?
• Give as many examples as you can for one point each of light behaving like a wave.
• Give as many examples as you can for one point each of light behaving like a particle.

Atomic and nuclear

• What did the Rutherford experiment establish about the structure of the atom?
• If most of an atom is empty space, why don't things like tables and people collapse?
• Explain why a simple planetary model of the atom fails?
• List some of the features of the Bohr model of the atom which cannot be explained by classical physics?
• Give as many examples as you can for one point each of an electron behaving like a wave.
• Give as many examples as you can for one point each of an electron behaving like a particle.
• Why do we need to describe electrons as waves?
• What is the photoelectric effect and why is it important?
• What are some of the features of the Bohr model of the atom which cannot be explained by classical physics?
• What does electron diffraction tell you about the nature of electrons?
• How can the spectrum of hydrogen have many lines (colors) although a hydrogen atom contains only one electron.
• What is meant by the wave/particle nature of an electron? (Aren't these two ways of viewing something incompatible?)
• What is Schrodinger's equation?
• What are the three types of radioactive decay?
• What is the difference between fusion and fission?
• What is a nuclear chain reaction?
• Give an example of a process which gives off energy by fusion.
• Why is a fusion reactor more desirable than a fission reactor?
• What element on the periodic table would best serve as fuel for a fusion reactor?
• What fuel would you use for a fusion reactor?
• How does carbon 14 dating work?
• Where do the elements heavier than helium (such as carbon, oxygen, etc.) of which we and the earth are made come from ?
• Name the four fundamental forces of nature.