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Consider the following statement. Earth is in the center
of the Universe, and everything is moving around it; using this model the motion
of most planets and stars can be calculated.
A) A reasonable, approximate model of the Universe
B) An ancient model, used for a millennium (but completely disagreeing with
modern observations)
C) Non-sense, nobody ever believed this. One cannot calculate anything this way.
D) A rather good, accurate theory.
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What is one of the "fundamental forces" (interactions)
A) friction B) reaction
C) gravity
D) there are many forces; none can be considered "fundamental"
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You go to a distant place in the outer space, where
you may consider that there is no gravity, air-resistance or any other forces.
You have two bricks, and know that one is made of lead, the other of aluminum;
aluminum has a much smaller mass. How can you determine which one is which ?
A) Estimate the weight in my hand; aluminum having a much smaller mass will
be much lighter.
B) Push them forward with the same force; aluminum will go faster.
C) Push them forward with the same force; aluminum will go slower.
D) Cannot determine it; would need more equipment to analyze the structure.
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When is a car's speed increasing ?
A) It takes longer and longer times to cover equal distances.
B) It covers equal distances in equal times.
A) Goes over longer and longer distances in equal times.
D) This car is described as accelerating; cannot answer without
knowing the actual speeds.
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You're at the airport on one of those moving sidewalks; it is moving with 3mph,
toward the North side of the building. You see a friend walking the other way
(to the South); she is going at 2mph. As you see her, you turn around and start
running, still on the sidewalk but opposite to where it moves (so, toward
the South), with 6 mph. Will you catch up with your friend ?
A) No
B) Yes; I am going 3mph faster
C) Yes, slowly; I am going only 1mph faster than she is
D) No – the sidewalk is still carrying me!
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You walk down the corridor; somebody passes you,
and keeps getting away, increasing the distance between you two.
A) His speed is greater than mine; his acceleration is not.
B) He accelerated, and keeps accelerating.
C) His speed is greater, but from this I cannot tell whether
he is accelerating.
D) He is not accelerating at all, just going faster.
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You stand on a very high tower and throw a ball horizontally. As it falls:
A) During equal times its speed downward increases by equal amounts
B) It is falling at a constant speed
C) It accelerates downward (as it starts falling), then falls with a constant speed
D) It accelerates downward; one cannot make any of the above statements about its
speed without doing a calculation.
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A ball is pushed so it rolls across the floor. Eventually the ball stops. Why?
A) The ball is coming to its natural state of rest.
B) Friction (or other resistive) forces bring the ball to a stop.
C) Since the push has stopped, the motion must also stop.
D) All motion must naturally stop in the absence of applied forces.
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Which of the following represents a case in which you are NOT accelerating?
A) Driving in a straight line at 60 miles per hour
B) Driving 60 miles per hour around a curve
C) Slamming on the brakes to come to a stop at a stop sign
D) Going from 0 to 60 miles per hour in 10 seconds
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A book is sitting still on top of the desk. Speaking
in terms of mechanics and gravity:
A) Altogether, no forces are acting, since it is not moving.
B) Gravity is there, but it cannot act through the desk.
C) Gravity cannot act because of the reaction of the desk.
D) There is gravity and the reaction; they add up to zero (exactly).
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Betty pushes on a table with 10N (Newtons) of force. Sally pushes on the
same table with 5N of force. What is the net force on the table due to
Betty's and Sally's pushes?
A) 15 N B) 5 N
C) 50 N D) 2 N
D) It depends on the direction they are pushing.
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Let us look at a bird, flapping its wings, flying. What are the forces acting
on it ?
A) Gravity, air resistance.
B) Just air resistance; the gravity has been overcome – the bird is flying.
C) Gravity, air resistance, reaction from air (pushing on its wings);
this is why it can fly
D) Gravity, no air resistance; this is how it flies, slipping through air.
E) No forces; upward pressure of air exactly cancels gravity (this is why it can fly)
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Because of gravity, the Earth exerts a force on a falling apple. How does this
force (on the apple) compare to the force the apple exerts on the Earth.
A) The two forces are exactly equal but opposite in direction.
B) The Earth exerts a large force on the apple, the apple a tiny force on the Earth.
C) The apple clearly exerts no force on the Earth.
D) The force of the Earth on the apple depends on the air resistance on the apple.
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A book is dropped and falling, due to the Earth's gravity.
A) The Earth is being accelerated toward the book,
too (but very little).
B) The book is accelerating; its action cannot accelerate, or otherwise move,
the Earth.
C) The book is falling at an even speed; no acceleration.
The Earth does not move.
D) The book accelerates; the Earth moves a little and then it stops.
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Suppose you lived on the Moon. Which of the following would be true?
A) Your weight would be less than your weight on Earth, but your mass would be the same
as it is on Earth.
B) Both your weight and your mass would be the same as they are on Earth.
C) Your mass would be less than your mass on Earth, but your weight would be the same
as it is on Earth.
D) Both your weight and your mass would be less than they are on Earth.
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Which one is NOT a type or form of, or cannot be
explained using, energy :
A) kinetic B) potential
C) throw D) heat
E) temperature
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A ball rolls on the floor and finally stops.
How does this fare with the law of "conservation of energy?"
A) It cannot be applied to a system with friction.
B) It states that energy can be converted into heat and internal energy;
this is what happens with the ball.
C) One can apply it to a rolling ball (without friction), and then
can do something else with the heat released.
D) Energy conservation is indeed a valid law, but only in some systems,
under rather specific conditions; for example, it cannot deal with
thermal losses.
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You take a balloon, measure its size and
the temperature of gas inside. Now you leave it in the direct
sunlight for a while, so the gas inside would warm up. Then
you measure it again, and find out that it expanded and got
warmer.
A) We made (some) use of the solar energy.
B) True; more precisely, this is the "conservation of energy."
(Except for the heating of the air part.)
C) This is precisely the "conservation of energy" law at work
(as in thermodynamics)
D) This shows that one has to be careful with "conservation
of energy;" this is an example of when this principle cannot
be applied by itself
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The balloon from the previous question ...
why would it expand ?
A) Well it doesn't have to expand; it may. The previous question
considers a case when it does.
B) Laws of physics : the gas inside gets warmer, so it moves faster,
and hits on the material of the balloon harder, pushing it outward
(a little).
C) The material the balloon is made of loosens up, because of
the sunshine's heat. (Gas is not hitting it from inside!)
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Energy will normally flow from hot to cold.
(An ice-cream in a pot of boiling water will melt.) What can you
say about this ?
A) Not true; the mentioned unfortunate ice-cream will melt, but
this is only one, special example.
B) It is a law of physics: spontaneously, energy is transferred
only from warmer to cooler.
C) This is indeed what we observe daily, but it is not quite a principle
of physics; there is a lot more to it.
D) Cannot make such statements; we would need to know a lot about
the microscopic behaviour.
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We are not happy with how efficient our machines
are. How much can we improve ?
A) Reduce the ever-present friction; this can, in principle, bring our
efficiency close to 100%
B) An ideal would be 100% efficiency; but it is so difficult to battle heat losses.
Once we will get there.
C) Can never get 100% efficiency, in principle; a law of physics
D) A better design; if we could use the concept of the "heat-engine," we
could, in principle, achieve even a 100% efficiency
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Which of the following is not thought of as an alternative
source of energy:
A) solar B) wind
C) oceans
D) refined garbage recycling
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How many (well-designed and controlled) experiments
does it take to prove a theory is false
A) just (a good) one : show that some statement from the theory does not hold
B) at least a few
C) It takes many experiments to test all the different variables.
D) No number of experiments can ever prove a theory to be false.
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Which of the following statements about scientific theories is not true?
A) A theory can never be proved beyond all doubt; we can only hope to collect more and more
evidence that might support it.
B) A theory is a model designed to explain a number of observed facts.
C) Scientists cannot take a theory seriously if it contradicts other theories developed by
scientists over the past several hundred years.
D) A theory must make predictions that can be checked by observation or experiment.
E) If even a single new fact is discovered that contradicts what we expect according to
a particular theory, then the theory must be revised or discarded.
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The most interesting thing in class so far this term has been: