Random Physics Question Part-2 ~ InSTaMeChEng

Question #1

The circuit photographed below includes three identical light bulbs and two identical batteries, wired as seen in the photograph. In this photograph the switch is OFF, that is, the circuit is open at that point. The intensity level of the two light bulbs is identical (well, almost in the photograph).

The question this week is: What will happen when the switch is turned ON, closing the circuit.
The upper light bulb will:

(a) become brighter.
(b) become dimmer.
(c) stay the same.

The lower light bulb will:

(a) become brighter.
(b) become dimmer.
(c) stay the same.

Question #2

Following up on the last Physics Question of the Week, we have another circuit problem.
The circuit photographed below includes two identical light bulbs and three identical batteries, wired as seen in the photograph. In this photograph the switch is OFF, that is, the circuit is open at that point. Notice that the intensity level of the two light bulbs is identical.

The question this week is: What will happen when the switch is turned ON, closing that part of the circuit circuit?
The upper light bulb will:

(a) become brighter.
(b) become dimmer.
(c) stay the same.

The lower light bulb will:

(a) become brighter.
(b) become dimmer.
(c) stay the same.

Question #3

Suppose that you support a meter stick horizontally by positioning one finger under one of the ends and the other finger about one-quarter of the way from the opposite end, as expertly demonstrated by Gwen in the photograph below.

Now suppose that Gwen moves her fingers slowly together until they touch. (The motion will be started in the configuration shown, with the meter stick extended off to the right side in the photograph.)
What will happen to the meter stick?

(a) It will fall off the right side in the picture above.
(b) It will fall off the left side in the picture above.
(c) Neither; it will end up balanced on Gwen's fingers.

Question #4

Three identical magnets, the orange rectangles, are stuck to a magnetic stainless steel disc as shown in the photograph below.

The disc will now be rotated, slowly at first and then at a faster and faster angular speed.
In what order will the magnets fly off the disc?

(a) outer, middle, inner.
(b) inner, middle, outer.
(c) all at the same time.

Question #5

A light dowel rod hangs by a string from a fixed point. The bottom end of the dowel rod rests on a frictionless surface, in this case a small piece of very light foam, that supports the end of the dowel on the surface of the water.

The drawings above illustrate three possible resting positions for the dowel. When the dowel is placed in one of the three positions and released, where will it finally come to rest?

(a) with its upper end beneath the support point.
(b) with its center of mass beneath the support point.
(c) with its lower end beneath the support point.

Question #6

A spring scale hangs from the top of a frame as shown in the figure at the left below. Attached to the bottom of the spring scale is a pulley; one end of the rope across the pulley is attached to the bottom of the frame, and the other end is free. Pulling on the free end of the rope creates a force on the spring scale.

When the frame is hung from a second identical spring scale, as shown in the figure at the right above, we see that the weight of the frame with its spring scale, pulley, and rope is about 5 Newtons.
With the frame hanging from the upper spring scale, the free end of the rope over the pulley in the frame is pulled until the lower spring scale reads 10 Newtons. When the lower spring scale reads 10 Newtons, what will the upper spring scale read?

(a) The upper scale will read 5 Newtons.
(b) The upper scale will read 10 Newtons.
(c) The upper scale will read 15 Newtons.

Question #7

Two light bulbs with different power (wattage) levels are attached in parallel (the usual way for household power distribution) across a 110 volt AC source. The higher power bulb (the larger bulb physically) glows more brightly, as seen in the photograph below.

Now suppose that the two bulbs are wired in series across the same 110 volt AC source. Which of the three possibilities given below will result?

(a) The larger bulb will glow more brightly.
(b) The smaller bulb will glow more brightly.
(c) The bulbs will be equally bright.

Question #8

A parallel plate capacitor consists of two equal and oppositely charged metal plates separated by a small distance, as seen in the photograph below. The voltage across the plates that created this charge separation on the plates is measured by the voltmeter in the picture, which is wired across the plates.

Now suppose that a thin circular, uncharged metal sheet, with the same diameter as the plates of the capacitor, is inserted between the plates of the capacitor. What happens to the voltage across the plates as measured by the voltmeter when the uncharged metal plate is inserted between the plates of the capacitor?

(a) The voltage across the plates will increase.
(b) The voltage across the plates will decrease.
(c) The voltage across the plates will remain the same.

Question #9

Most people are familiar with the standard "collision balls" apparatus. Six identical steel balls are suspended in a row; lifting one of the end balls and releasing it causes the one on the opposite side to move away, then fall back, causing the original ball to do the same, etc. This action can be seen on an mpeg video by clicking your mouse on the photograph below. The motion satisfies all of the requirements of conservation of energy and linear momentum during the various collision processes.

Now suppose that we modify this apparatus, as seen in the photograph below, so that one of the balls (the fourth from the left) is made from aluminum rather than steel, and therefore no longer has the same mass.

In this case, how will the collision balls apparaus work? In particular, will it work the same way as the equal mass collision ball apparatus? Will the ensuing motion be one ball moving up on one side, then the other side, back and forth?

(a) Yes!
(b) No!

Question #10

Gwen is holding a rather heavy set of keys attached to a very light cardboard matchbook by a light string, with the keys hanging over her finger by only a few inches of string, as seen in the photograph below. She will release the matchbook from rest in the position shown.

The question is what will happen when the matchbook is released.
One possibility is that the keys will fall to the floor because they are very heavy compared with the rest of the system. Another possibility is that the matchbox will start to fall, and because of the long string it will exert a lot of "centrifugal force" on the keys and pull the keys back over Gwen's finger. A third possibility is something in between these extremes. Perhaps the torque exerted by the matchbox end of the string will counterbalance the inertia of the keys, causing the system to stop with the string over Gwen's finger (does this make any sense?). If neither the keys nor the matchbox pulls the other over Gwen's finger, exactly what will happen?
So what will happen when Gwen releases the matchbox?

(a) The keys will fall, pulling the matchbox over Gwen's finger.
(b) The matchbox will pull the keys over Gwen's finger.
(c) Neither of the above.

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InSTaMeChEng

Monday, 2 September 2013