Three objects of equal mass, A, B, and C, are released from rest at the same instant from the same height

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Three objects of equal mass, A, B, and C, are released from rest at the same instant from the same height on identical ramps

Three objects of equal mass, A, B, and C, are released from rest at the same instant from the same height on identical ramps. Objects A and B are both blocks, and they slide down their respective ramps without rotating. Object C rolls down the ramp without slipping. Its moment of inertia is unknown.
Objects A, B, and C are made of different materials, thus the coefficients of friction between the objects and their coffesponding ramps are not necessarily the same.

Object A reaches the bottom of its ramp first, followed by objects B and C, which reach the bottom at the same instant.
a. Rank the objects according to magnitude of center-of-mass acceleration, from largest to smallest. If any objects have the same magnitude center-of-mass acceleration, state so explicitly. Explain.
b. Rank the net forces exerted on the three objects according to magnitude, from largest to smallest. If the net force on arly two objects is the same, state so explicitly. Explain.
c. In the spaces provided, draw and label a (point) free- body diagram for each object.
Free-body diagraur for object i
F-ree-bocly dia*uram
for object B Free-body diagram
for object C
d. Rank the frictional forces exerted on the three objects according to magnitude, from largest to smallest. If the magnitude of the frictional force is the same on any two objects, state so explicitly. Explain your reasoning.

5. Energy analysis of falling-spools experiment
The modified Atwood’s machine shown at right consists of two identical spools connected by a massless, ‘ ” inextensible thread that runs over an ideal pulley. The thread is wrapped around spool A many times, but it is attached to a fixed point on spool B, so that spool B will not rotate.
The spools are released from rest from the same height at the same instant.
a. In tutorial, you observed the motion of the spools after they were released. Ignoring small dffirences in their nntions:
. In which direction did each spool move?
. Did spool A hit the ground before, after, or at the same instant as spool B?
Is the mngnitude of the center-of-nutss acceleration of spool A (while it is fallin g) greater than,less than, or equal to that of spool B? Explain.
Is the translational kinetic energy of spool A just before it hits the ground greater thsn, less than, or equal to that of spool B? Explain.
d. Is the total kinetic energy of spool A just before it hitsothe ground greater than, less than, or equal to that of spool B? Explain.
Consider the system consisting of all of these objects: spool A, spool B, the thread, the pulley, and the Eafth.
i. Explain how you can tell that the total energy of this system(i.e., Ugnv,o+ Ug^”,n * Kton,,e * K,*nr. n * Kro’ a, * K,o’ s) is constant as spools A and B fall.
b.
c.
Suppose that this system starts with Ugo”, o = f/srr, B = 9 J. Just before the spools hit the ground, which is where the zero for gravitational potential energy is chosen, spool A has translational kinetic energy K,on,”a = 4 J. Determine the value of the rotational kinetic energy of spool A at this instant. Show your work.
A third identical spool, spool C, is added to the falling-spools experiment described in the preceding problem.
As above, all spools are released from rest from the same height at the same instant. Spool C is not in contact with any other objects as it falls.
a, Rank the spools according to magnitude of center -of-mas s acc eleration (while falling), from largest to smallest. If any spools have the same center-of-mass acceleration, state so explicitly. Explain.
b. As in the preceding problem, suppose that Ugrrr. n = Ugr,, s = 9 J before the spools are released. Just before the spools hit the ground, which is where the zero for gravitational potential energy is chosen, spool A has trarrslational kinetic energy K,*,, e,= 4J.
i. Rank the spools according to maximum tanslatianal kinetic energy, from largest to smallest. If any spools have the same maximrrtn translational kinetic energy, state so explicitly. Explain. (Use the definition K*, = lma”^’.)
ii. Rank the spools according to maximum total kinetic energy, from largest to smallest. If any spools have the same maximum total kinetic energy, state so explicitly. Explain.

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After a hockey player gives a puck a quick ‘hit’ with his stick, the puck slides across the ice at a speed that is essentially constant. A student in a previous class offered the following force diagram and explanation for why the speed of the puck is constant after the hit. What is your evaluation of this explanation?

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After a hockey player gives a puck a quick ‘hit’ with his stick, the puck slides across the ice at a speed that is essentially constant. A student in a previous class offered the following force diagram and explanation for why the speed of the puck is constant after the hit.
What is your evaluation of this explanation?
“The initial hit exerts a force on the puck, making the forces acting on the puck unbalanced, and so it starts to move. After the hit ends there is no net force acting on the puck, and when the net force acting on an object is zero, its speed does not change. So after the stick has lost contact with the puck, its speed remains constant.”
Select one:
a. Both the force diagram and the narrative are problematic.
b. The force diagram is problematic but the narrative is accurate.
c. Both the force diagram and the narrative are accurate.
d. The force diagram is accurate but the narrative is problematic.
Frank and Hector are moving two boxes across a rough floor. Frank pushes a 20 kg box with a force of 85 N while a frictional force of 75 N acts on it in the opposite direction. Meanwhile, Hector pushes on the 30 kg box with a force of 105 N while a frictional force of unknown strength acts on it.
Frank and Hector find that as their boxes are moving, they remain side-by-side, so they realize they must both be changing speed at the same rate. What is the strength of the frictional force acting on the 30 kg box?
Select one:
a. 90 N
b. 95 N
c. 75 N
d. 93 N
When shopping for a new car, a professor was surprised to learn that a certain small compact car (mass=800 kg) will speed up (accelerate) at a faster rate than a large SUV (mass=2200 kg), although the SUV has the more powerful engine.
What is the reason that the compact car can speed up at a faster rate than the SUV, despite having a less powerful engine?
Select one:
a. The quantity pushing force / mass is greater for the compact car.
b. The quantity pushing force / mass is smaller for the compact car.
c. The quantity pushing force * mass is smaller for the compact car.
d. The quantity pushing force * mass is greater for the compact car.

You have likely experienced a static ‘shock’ after walking across a carpet, just as John Travoltage did in the simulator. Which of the following best explains why this is much more likely to happen on a cold, dry, winter’s day than a warm, humid, summer’s day?

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You have likely experienced a static ‘shock’ after walking across a carpet, just as John Travoltage did in the simulator. Which of the following best explains why this is much more likely to happen on a cold, dry, winter’s day than a warm, humid, summer’s day?
Select one:
a.
Negative charges are transferred to you from the carpet on both warm and cold days, but these excess negative charges do not remain on you. Instead, they are removed almost immediately by humid air.
b.
Humid air does not undergo ‘breakdown’ so the charges do not transfer to the doorknob until you touch it.
c.
Negative charges are transferred to you from the carpet on a cold day, but not on a warm day.
16- Consider the following situation. Suppose a – charged object were placed above an uncharged non-metal object. Which of the diagrams shown and described below would best represent the polarization of the atoms in the non-metal object?
Select one:
Diagram A
Diagram B
Diagram C
17- If you rub a balloon against your hair, the balloon becomes negatively charged. If you then hold the rubbed part of the balloon against a wall and let go, assuming the conditions are not too humid, the balloon will stay ‘attached’ to the wall, at least for a short while.
Which one of the following four diagrams would most accurately represent how the charges in the wall are arranged after the balloon comes into contact with the wall?
Select one:
Choice A
Choice B
Choice C
Choice D

Given what you have learned in this extension, which of the following would be the most appropriate assumption to make in a model that uses charged entities to explain static electric effects?

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Given what you have learned in this extension, which of the following would be the most appropriate assumption to make in a model that uses charged entities to explain static electric effects?
Select one:
a.
Both negatively (–) and positively (+) charged entities can move through materials and be transferred to other objects.
b.
Positively (+) charged entities can move through materials and be transferred to other objects, but negatively (–) charged entities cannot move.
c.
Negatively (–) charged entities can move through materials and be transferred to other objects, but positively (+) charged entities cannot move.
11- Suppose you had a positively (+) charged object that you wanted to make uncharged. Which would be the easiest way to do so?
Select one:
a.
Add some electrons to it.
b.
Both A and B would be equally easy.
c.
Remove some protons from it.
11- According to the reasoning you applied in the second part of this assignment, when the Styrofoam plate and acrylic sheet have been rubbed together, how does the acrylic sheet acquire a positive charge?
Select one:
a.
Some combination of A, B, C, and D occurs.
b.
Positive (+) charges are created on the acrylic sheet.
c.
The acrylic sheet transfers negative (–) charges to the Styrofoam plate.
d.
Negative (–) charges are destroyed on the acrylic sheet.
e.
The Styrofoam plate transfers positive (+) charges to the acrylic sheet.
12- Taking account of what they learned in this homework assignment a group of students drew these diagrams to represent their revised model for what happens when an acrylic sheet and a Styrofoam plate are rubbed together.
Is there a problem with this model? if so, what is it?
Select one:
a.
The problem is that negatively (–) charged entities have moved.
b.
The problem is that it does not obey the Law of Conservation of Charge.
c.
There are no problems with this model.
d.
The problem is that no positively (+) charged entities have moved.
13- Which of the following is most appropriate to describe what happens when a person discharges a negatively (–) charged object by touching it?
Select one:
a.
Positive charges pass from the object to the person.
b.
Positive charges pass from the person to the object.
c.
Negative charges pass from the person to the object.
d.
Negative charges pass from the object to the person.
14- Which of the following is most appropriate to describe what happens when a person discharges a positively (+) charged object by touching it?
Select one:
a.
Negative charges pass from the person to the object.
b.
Positive charges pass from the person to the object.
c.
Negative charges pass from the object to the person.
d.
Positive charges pass from the object to the person.

Given what you have learned in this extension, which of the following would be the most appropriate assumption to make in a model that uses charged entities to explain static electric effects?

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Given what you have learned in this extension, which of the following would be the most appropriate assumption to make in a model that uses charged entities to explain static electric effects?
Select one:
a.
Both negatively (–) and positively (+) charged entities can move through materials and be transferred to other objects.
b.
Positively (+) charged entities can move through materials and be transferred to other objects, but negatively (–) charged entities cannot move.
c.
Negatively (–) charged entities can move through materials and be transferred to other objects, but positively (+) charged entities cannot move.
11- Suppose you had a positively (+) charged object that you wanted to make uncharged. Which would be the easiest way to do so?
Select one:
a.
Add some electrons to it.
b.
Both A and B would be equally easy.
c.
Remove some protons from it.
11- According to the reasoning you applied in the second part of this assignment, when the Styrofoam plate and acrylic sheet have been rubbed together, how does the acrylic sheet acquire a positive charge?
Select one:
a.
Some combination of A, B, C, and D occurs.
b.
Positive (+) charges are created on the acrylic sheet.
c.
The acrylic sheet transfers negative (–) charges to the Styrofoam plate.
d.
Negative (–) charges are destroyed on the acrylic sheet.
e.
The Styrofoam plate transfers positive (+) charges to the acrylic sheet.
12- Taking account of what they learned in this homework assignment a group of students drew these diagrams to represent their revised model for what happens when an acrylic sheet and a Styrofoam plate are rubbed together.
Is there a problem with this model? if so, what is it?
Select one:
a.
The problem is that negatively (–) charged entities have moved.
b.
The problem is that it does not obey the Law of Conservation of Charge.
c.
There are no problems with this model.
d.
The problem is that no positively (+) charged entities have moved.
13- Which of the following is most appropriate to describe what happens when a person discharges a negatively (–) charged object by touching it?
Select one:
a.
Positive charges pass from the object to the person.
b.
Positive charges pass from the person to the object.
c.
Negative charges pass from the person to the object.
d.
Negative charges pass from the object to the person.
14- Which of the following is most appropriate to describe what happens when a person discharges a positively (+) charged object by touching it?
Select one:
a.
Negative charges pass from the person to the object.
b.
Positive charges pass from the person to the object.
c.
Negative charges pass from the object to the person.
d.
Positive charges pass from the object to the person.

Below are images and descriptions of three different arrangements of charges from the ‘Electric Field Hockey’ simulation. Which one of these would result in a goal being scored when the positively-charged puck is released?

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Below are images and descriptions of three different arrangements of charges from the ‘Electric Field Hockey’ simulation. Which one of these would result in a goal being scored when the positively-charged puck is released?
Select one:
Arrangement A
Arrangement B
Arrangement C
6- The arrangement below from the ‘Electric Field Hockey’ simulator shows a negatively (­–) charged puck in front of the goal. Directly behind the goal is a line of three charges (–, +, ­–), with a second + charge directly behind the first.
How would the negatively-charged puck behave when it is released, and why?
Select one:
a.
It would not move toward or away from the goal because there are equal numbers of + and – charges behind the goal.
b.
It would be attracted toward the goal because the + charges are both in the middle of the arrangement.
c.
It would repelled away from the goal because taken together, the two negative charges are nearer to it than the two positive charges.
7- When you bring a small object close to a charged tape you find that there is an attraction between them. Considering all the evidence you saw in early in this unit, what can you conclude about the charge of the small object?
Select one:
a.
It has the opposite charge to the tape.
b.
It is uncharged.
c.
Either B or C could be true.
d.
It has the same charge as the tape.
8- In another class, a student drew a diagram and gave an written explanation for what happens when a negatively-charged Styrofoam plate is brought near a soda can electroscope.
Before the plate is brought close to the base end of the soda can electroscope, the positive and negative charges are uniformly distributed in the soda can and the tinsel, and both ends of the soda can are uncharged. When the negatively (–) charged Styrofoam plate is brought next to the electroscope, all of the positive charges in the soda can (and the tinsel) move toward the negatively charged plate because of the Law of Electric Charges, which states that opposite charges attract. All of the negatively charged particles move toward the tinsel end, and into the tinsel, because like charges repel. For that reason, the negatively-charged pieces of tinsel repel each other.
Question 1)
Evaluate the student’s model.
Can the diagram and the written explanation account for the evidence presented in the experiment and simulation movies that you watched in this extension?
Select one:
a.
The diagram can account for the evidence provided by the movies, but the written explanation cannot.
b.
Neither the diagram nor the written explanation can account the evidence provided by the movies.
c.
The written evidence can account for the evidence provided by the movies, but the diagram cannot.
d.
Both the diagram and the written explanation can account for the evidence provided by the movies.
9- Which of the following pieces of evidence should lead the student to change her model (either the diagram, the written explanation, or both)? Choose all answers that apply.
Select one or more:
a.
Evidence or separate knowledge that, while both types of charges can move, they can only move a very short distance in the soda can.
b.
Evidence or separate knowledge that the middle portion of the soda can (between the top and base) is uncharged when the negatively-charged plate is held near the base end.
c.
Evidence that a positively-charged object attracts the tinsel, when the negatively-charged plate is held close to the electroscope’s base side.
d.
Evidence or separate knowledge that only one type of charge (either + or –) can actually move in the electroscope, rather than both types (+ and -) of charges moving.
e.
Evidence that a negatively-charged object repels the tinsel (pushes the tinsel strands together), when the negatively-charged Styrofoam plate is being held close to the electroscope’s base side.