Random Physics Paradox Questions :-)

PHYSICS IS AWESOME. Every thing in the world has some physics applied to it in some way or the other.Enjoy solving these questions and do check the answers available at the downloads.

Question #1

Consider the frame device with arms as shown in the three figures below. Note that it will remain at rest in any of the three positions shown if it is moved to that position and released.
Equal masses of 200 grams are positioned on the arms as shown below, and the device is held so that it can not move.
When the arm is released, which of the following will happen?

• (a) The left side will go down.
• (b) The right side will go down.
• (c) Neither side will go down: it will remain horizontal.

Question #2

Identical balls are launched at the same time with the same velocity from the left front end of the two-track gizmo photographed below. (Because this is a physics problem, there is no friction.) A race of the balls will then ensue. The ball on the flat track clearly proceeds across the track at a constant speed. The ball on the dipped track goes for a while at that same speed, goes faster while it is in the dipped part of the track, then returns to its original speed for the final segment of the track. Note that it also travels further.
What will happen?

• (a) The ball on the straight track will reach the end first.
• (b) The ball on the track with the dip will reach the end first.
• (c) The race will end in a tie.

Question #3

A ball floats on water, as seen in the photograph below, but will sink when put into mineral spirits. The water is dyed green with food coloring to distinguish it from the clear mineral spirits. Note how far the floating ball sinks into the water.
When the mineral spirits is poured slowly onto the top of the water, it will remain on top because the two fluids are immiscible.
If the mineral spirits is poured slowly on top of the water while the ball is floating on the water, what will happen to the level at which the ball floats?

• (a) The ball will float lower into the water.
• (b) The ball will float higher out of the water.
• (c) The ball will float at the same level with respect to the surface of the water after the mineral spirits are poured on top of the water.

Question #4

The figure below shows three parallel horizontal light rays moving from left to right, passing through a rectangular block of plexiglass and focused to a point by a plexiglass lens. The focal point is marked by a large dark dot.

If the rectangular block is rotated counterclockwise, the rays will be displaced upward, but continue on parallel to each other and horizontal, as seen in the figure below with the lens removed. Note that the vertical position of the focus (the dot) is along the lower of the three rays.

Now suppose that the lens is left in place when the rectangular block is rotated. What will happen to the position of the focus?

• (a) The focus will move UPWARD.
• (b) The focus will move DOWNWARD.
• (c) The focus will remain in the same position.

Question #5

Two identical balloons are filled unequally with air and connected to opposite ends of a short plastic tube, as shown in the photograph below. A clamp is positioned on the upper (smaller) balloon so that no air can flow between the balloons, even if it wanted to.
What will happen when the clamp is released, allowing air to flow, if it wants to?

• (a) The small balloon will get smaller, and blow up the big one.
• (b) The balloons will become the same size.
• (c) The balloons will stay the same as they were before the clamp was released.

Question #6

A funnel cart, as seen in the photograph below, consists of a cart with a funnel mounted on it. It is constructed with frictionless wheels (We can do this in physics.) so that it will roll with a constant speed along the straight level track in the photograph. A spring in the funnel can be compressed so that if a ball is placed in the funnel, and the funnel then compressed and released, the ball will be ejected directly up and fall back into the funnel. The ball is HEAVY, so air resistance is negligible.
When the cart is pushed from left to right along the track, a trip on the track hits a cam connected to the funnel, ejecting the ball when the cart gets to the location at which it is shown in the picture below, as the cart moves along the track.
When the ball is ejected in this manner, where will it fall?

• (a) The ball will fall in front of the funnel.
• (b) The ball will fall behind the funnel.
• (c) The ball will fall IN the funnel.

Question #7

In Question #6, we saw how a funnel cart works when the track is horizontal with the cart moving at a constant velocity. You may want to review Question and Answer #6 before doing this question.
Now suppose that the cart is attached to a string running over a pulley at the right end of the track with a weight hanging on the end, as shown in the picture below.

When the cart is held at the left end of the track and released, it accelerates across the track, with the ball ejected when it gets to the same point as before. Where will the ball land?

• (a) The ball will fall in front of the funnel.
• (b) The ball will fall behind the funnel.
• (c) The ball will fall IN the funnel.

Question #8

In Questions #6 and #7, we saw how a funnel cart works when the track is horizontal. For this question we will investigate what happens when the track is tilted. Before attempting this question you may want to review the questions for the previous two weeks.
Now suppose that the track is tilted, as shown in the figure below, so the cart is accelerating down the incline when it gets to the point on the track at which the ball is ejected - this time perpendicular to the track.

Where will the ball fall this time?

• (a) The ball will fall in front of the funnel.
• (b) The ball will fall behind the funnel.
• (c) The ball will fall IN the funnel.

Question #9

A plastic SLINKY is held by one end and allowed to hang freely, as shown in the photograph below.
If the top end of the SLINKY is released, allowing it to fall, it will eventually end up totally collapsed and lying on the floor. When it is released two actions will occur simultaneously - it will move toward the floor and it will collapse. This question involves the manner in which it falls, and in particular what the bottom end does when it begins to fall.
When the SLINKY is held by the top end and released, what will bottom end do initially?

• (a) The bottom end will move up initially.
• (b) The bottom end will move down initially.
• (c) The bottom end will remain at the same point for a short time before it begins to move.

As part of this problem, see if you can predict exactly how the SLINKY will fall.

Question #10

A beaker of water is in equilibrium with 300 grams of steel mass on a pan balance, as shown in the photograph below.

Now suppose that you slowly insert your finger into the water up to the first knuckle, being careful not to touch the beaker. What will happen to the equilibrium condition of the pan balance?

• (a) The side with the water will go down.
• (b) The side with the weights will go down.
• (c) Neither side will go down; the pan balance will remain in equilibrium.

Question #11

Which is faster, rolling or sliding? Consider the two almost identical aluminum cylinders in the photograph at the left below. One rolls without sliding, while the other slides without friction (to a good approximation) on four tiny ball bearings mounted at one end of the cylinder.

Suppose that they are started simultaneously from rest at the top end of an inclined plane, one rolling down the incline and the other sliding without friction, as shown in the photograph at the right above.
As they race down the incline, what will happen?

• (a) The rolling cylinder will get to the bottom of the incline first.
• (b) The sliding cylinder will get to the bottom of the incline first.
• (c) They will get to the bottom at the same time; the race will end in a tie.

Question #12

The words "CHOICE MATERIAL GLASS OXIDE" are printed in block letters, with "CHOICE" and "OXIDE" in red and "MATERIAL GLASS" in blue. These words are photographed in the top half of the figure below. When the words are photographed through a glass rod immediately in front of them their appearance changes somewhat, as can be seen in the bottom half of the figure. (The top photograph is a view looking over the glass rod at the letters.)
The question is what is responsible for this rather unusual phenomenon?

• (a) The dispersive effect of the difference in color causes the focusing properties of the rod to be different from red to blue.
• (b) The rod might be different between the red and the blue letters, causing the focusing to change.
• (c) Polarization may play an important role in causing differences in internal reflectivity that lead to different focal properties.
• (d) Other.

Question #13

When light collimated by a slit passes through a prism and is focused on a screen the well-known spectrum of white light is produced; this is shown in the photograph at the right below. The experimental setup, photographed at the left below, consists of a bright light source, a baffle with the slit immediately in front of the light, a prism, and a lens, just before the prism, to focus an image of the slit onto the screen, seen at a distance in the photograph. The image is purpusely washed out in the photograph.

If you pass light through the prism and focus it on the screen without a defining slit, it creates a wide white band with a blue color at the maximum angle of bend and a red color on the minimum angle of bend, as shown in the photograph below.

Suppose that the slit is "inverted" so that the opening becomes opaque and the material surrounding the slit becomes transparent, creating a sort of "negative" slit. In the figure below these three "slit" configurations are photographed: from bottom to top, the regular slit, the "negative" slit, and no slit.

When you create a "spectrum" using the "negative" slit, how will the spectrum displayed on the screen be changed, if at all?

• (a) The spectrum will be the same.
• (b) The spectrum will have colors complementary to the original white light spectrum.
• (c) The light on the screen will be white.
• (d) There will be a faint spectrum superposed on the brighter white background.

Question #14

The photograph below shows a graduated cylinder containing blue water and a spherical flask.
If you pour the water from the graduated cylinder into the flask, which of the following statements will be true?

• (a) The water will not fill up the sphere.
• (b) The final water level will be somewhere in the cylindrical neck of the flask.
• (c) The water in the cylinder will not fit into the flask.

Question #15

A microwave transmitter (at the right in the photograph at the left below) produces approximately 12cm wavelength microwaves which are picked up by the receiver (at the left in the photograph), with the amplitude of the microwave signal voltage at the receiver displayed by the meter in the background (center zero, reading about 30 units). Note that both the transmitter antenna and the receiver antenna are oriented vertically, so the microwave vibration is vertical, and the waves are vertically polarized.
Now suppose that a wire rack like a cookie cooler, shown in the photograph at the right, is lowered into the beam between the transmitter and the receiver. The polarization of the microwaves and the orientation of the wires are both in the same direction (vertical). Which of the following statements about the signal voltage at the receiver will be true?

• (a) The intensity of the microwaves will go up significantly.
• (b) The intensity of the microwaves will go down significantly.
• (c) The intensity of the microwaves will remain approximately the same.

Question #16

Before launching into the question, let us review how a standard mercury barometer works.
First a tube, over 76 cm in length and sealed on one end, is filled completely with mercury (the heavy liquid) and it is then positioned vertically with the open end in a pool of mercury. Atmospheric pressure will then hold the mercury up in the tube at a height such that the downward pressure exerted by the mercury in the tube on surface of the mercury pool is equal to the atmospheric air pressure, also exerted downward on the surface of the mercury pool. As the atmospheric pressure rises and falls, the level of the mercury in the tube rises and falls, so that the numerical value of the air pressure at any given time is equal to the height of the mercury column.
We have made a sort of barometer using a short water column with a beaker of water as the pool, only the tube of our barometer is supported by a spring scale, as seen in the photograph below. Blue water taken from the azure seas of the Caribbean is used because it is easier to see. Notice the "weight" of the tube as shown by the scale; this is equal to the upward force required to hold the tube up.

Now suppose that we remove a small seal at the top of the tube, allowing outside atmospheric air to enter the tube and displace the water, so there will be air rather than water in the tube. The question involves the force necessary to hold up the tube after the water in the tube has drained out.
Which of the following statements most accurately describes the situation after the water in the tube has drained out into the beaker?

• (a) The reading of the spring scale will be greater.
• (b) The reading of the spring scale will be less.
• (c) The reading of the spring scale will remain the same.

Question #17

Suppose that you are in a boat in a closed pond, so no water can flow in or out of the pond. In your boat you have a large rock. A friend marks the water level on the side of the pond, then you throw the rock out of the boat into the pond, and it quickly sinks to the bottom. A model of this situation is shown below, where the boat floats in an aquarium with a lead weight rock; pieces of black tape mark the water level.
Which of the following statements most accurately describes what happens to the water level in the pond after the rock has been taken out of the boat and allowed to sink into the pond?

• (a) The water level in the pond will be higher.
• (b) The water level in the pond will be lower.
• (c) The water level in the pond will remain the same.

Question #18

Gwen seems a bit perplexed as she views her image in the plane (flat) mirror.
She is perplexed because she cannot figure out exactly how to describe her image in the mirror. So that is the question for this week.
When you view your image in a plane mirror, is your image

• (a) inverted top-to-bottom?
• (b) inverted left-to-right?
• (c) inverted front-to-back?
• (d) not inverted at all?

Question #19

Now that you have a good understanding from Question #18 of the image created by a plane mirror, consider the related problem: Suppose that you hold the transparency in the photograph below in front of a mirror.

How will its reflection appear? Is the image:

• (a) inverted top-to-bottom?
• (b) inverted left-to-right?
• (c) inverted front-to-back?
• (d) not inverted at all?

Write out the word LIGHT as it will appear in the mirror.

Question #20

Two rubber o-rings are tightly fitted onto a section of thin-walled aluminum tube, as shown in the photograph below. This device rests on a long strip of thin plastic, as seen in the photograph.

The plastic strip is held horizontal, along the surface of the table, and rapidly pulled out from under the cylinder. Because there is a lot of friction between the o-rings and the plastic sheet, pulling the sheet out from under the cylinder causes the cylinder to spin rapidly in the clockwise direction and to move from right to left in the picture above.
After the plastic sheet has been pulled out from under the cylinder, and the cylinder comes into contact with the table top, which of the following will happen?

• (a) The cylinder will roll to the left.
• (b) The cylinder will roll to the right.
• (c) The cylinder will stop and remain near where it was when it left the plastic.

ANSWERS 1-10 QUESTIONS:

ANSWERS 11-20 QUESTIONS:

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