in class with chris d’amato - Latest Comments

Re: xkcd ftw

incognito — Thu, 31 Mar 2011 19:08:15 -0000

Owned. FTW

Re: Touch trigonometry

chrisdamato — Tue, 18 Jan 2011 11:08:23 -0000

Come talk about how you will rewrite it in html5 or even geogebra: Geek lounge

Re: Touch trigonometry

Gridcbug — Tue, 18 Jan 2011 09:18:05 -0000

If not for the inherent awesomeness, I would rage at the flashbomb.

Re: A coloring puzzle

Hksmytimenow — Fri, 31 Dec 2010 18:32:21 -0000

3. i win.

Re: A coloring puzzle

MJ Arteaga — Sat, 13 Nov 2010 15:51:18 -0000

4. because each circle is connected to 3 other circles by lines, and you need to paint the original with one color, so 4 different color sis the minimun.

Re: Exam resources

edan — Thu, 04 Nov 2010 13:44:16 -0000

3? top one is A, then traveling in this direction ---> B, C, A, B (<---outer circles) then where the first A is put a B under it and Traveling in the same direction ---> C then A, B, C. none should be touching unless my directions are wrong
p.s. Letters Represent colors

Re: A coloring puzzle

Chris D'Amato — Sat, 23 Oct 2010 06:30:44 -0000

You can play with this easily using the paint bucket tool in your image editor of choice ... just right-click and save the image, or whatever you do on a mac.

Re: Dynamics Test: Q25-Q28

julijanabajceska — Mon, 04 Jan 2010 18:30:30 -0000

Test question: 26
Original Answer Choice: 1- The force exerted by the car pushing against the truck is equal to that exerted by the truck pushing back against the car. **CORRECT**
Original Reasoning: Even though the car is pushing the truck and is speeding up, does not mean that the force exerted on the truck is greater than the force exerted on the car. The forces exerted are equal.

Re: Dynamics Test: Q5

BrittanyHunter — Mon, 04 Jan 2010 18:28:30 -0000

Original Choice: 1
Original Reasoning: I thought that the object wiuld stop immediately when the force upon it is eliminated.
New Answer Choice: 3
New Reasoning: I know now that the object has an initial force, would allow it to keep moving and thus eliminate answer number one. The object will instead immediately start slowing to a stop, decelerating, due to its initial force. In no way would the object increase its speed because there was not an increase in force.

Re: Dynamics Test: Q20-Q24

julijanabajceska — Mon, 04 Jan 2010 18:26:31 -0000

Test question: 22
Original Answer Choice: THe truck exerts the same amount of force on the car as the car exerts on the truck. **CORRECT**
Original Reasoning: Just as speed does not matter in the amount of force exerted, neither does size. Just because one object is bigger and/or heavier than the other does not mean it exerts more force. No matter what, both the truck and the car will exert the same amount of force on to the other. I agree with the two students above.

Re: Dynamics Test: Q20-Q24

julijanabajceska — Mon, 04 Jan 2010 18:23:31 -0000

Test question: 20
Original Answer Choice: 5- THe truck exerts the same amount of force on the car as the car exerts on the truck. **CORRECT**
Original Reasoning: Although one may think that because they are moving at the same speed that the forces are the same, this thinking is incorrect. No matter what speed the car and truck go, they will still exert the same amount of force onto the each other.

Re: Dynamics Test: Q4

BrittanyHunter — Mon, 04 Jan 2010 18:20:03 -0000

Test Question: Q4
Original Answer Choice: 4
Original Reasoning: This was my original response because I assumed that there was an unbalanced force, thus resulting in the box moving.
New Answer Choice: 3
New Reasoning: My original answer could have been correct, but the problem states that the box is moving at a constant speed, which means that it is not accelerating. Therefore there are no unbalanced forces and the forces exerted are equal.

Re: Dynamics Test: Q9-Q14

julijanabajceska — Mon, 04 Jan 2010 18:15:30 -0000

Test question: 11
Original Answer Choice: 5 **CORRECT**
Original Reasoning: Because of the fact that the Voyager spacecraft is "very far away from the Earth, Sun, and the other planets, there will not be any force of Earth upon the object. Also, nothing else is interacting with the spacecraft. So, the correct answer has to be choice 5.

Re: Dynamics Test: Q9-Q14

julijanabajceska — Mon, 04 Jan 2010 18:12:56 -0000

Test question: 10
Original Answer Choice: 1 **CORRECT**
Original Reasoning: Considering the ball is at rest in your hand the only two forces that are interacting with the ball is your hand and Earth. It is also and equilibrium because the ball is not moving. Therefore, the answer to question 10 is choice 1.

Re: Dynamics Test: Q9-Q14

julijanabajceska — Mon, 04 Jan 2010 18:09:55 -0000

Test question: 9
Original Answer Choice: 4
Original Reasoning: I originally thought that considering a person is in the air, the only force interacting with him/her is the Earth.
New Answer Choice: 3
New Reasoning: While looking at force diagram 3, one realizes that the force of the Earth is longer than the other force that is interacting with the person. This may be what causes the person to fall back down.

Re: Dynamics Test: Q3

julijanabajceska — Mon, 04 Jan 2010 18:03:14 -0000

Original Answer Choice: 5
Original Reasoning: Newton's Third Law states that for every action there is an equal and opposite reaction. In the problem, Bob pushes Jim while having his feet on Jim's knees. Considering the two objects, (Bob and Jim), are interacting, Newton's Third Law applies to this problem. I agree with the students above.

Re: Dynamics Test: Q2

julijanabajceska — Mon, 04 Jan 2010 17:57:24 -0000

Test question: 2
Original Answer Choice: 3 **CORRECT**
Original Answer Reasoning: In the problem, it states that each time the force exerted on the TV box is increased. Considering the mass of the box stays the same, the acceleration has to increase as well. Therefore it rules out answers 1 and 4. By looking at graphs 2 and 3, one sees that 2 does not start at 0 but 3 does. The box is initially at rest, so the answer has to be 3.

Re: Dynamics Test: Q15-Q19

alexgonzalez — Mon, 04 Jan 2010 17:55:44 -0000

Thank youuu kyle!

Re: Dynamics Test: Q15-Q19

alexgonzalez — Mon, 04 Jan 2010 17:55:11 -0000

Thanks so much your comments really help!

Re: Dynamics Test: Q1

KevinCampo — Mon, 04 Jan 2010 15:49:46 -0000

The answer to number 1 is 2. The reason for this is because the forces exerted on the book are the earth and the table. The earth's force would be down and the force of the table would be going up.

Re: Dynamics Test: Q30

melissaberardi — Mon, 04 Jan 2010 00:24:41 -0000

Test Question: Q30

Original Answer Choice: [1] - The sled moves in the negative direction at a constant velocity. **Incorrect**

Original Reasoning: I thought that the sled would move in the negative direction because of the negative force acting upon it and that it would have a constant velocity because the strength of the force was unchanging.

New Answer: [2] - The sled moves in the negative direction and the sled's speed is increasing at a constant acceleration.

New Reasoning: I now understand that I was correct in my thinking that the sled would move in the positive direction but that the sled would be moving at a constant acceleration. This would be because of the mass of the sled not changing, along with the net forces of the sled not changing.

Re: Dynamics Test: Q29

melissaberardi — Mon, 04 Jan 2010 00:20:54 -0000

Test Question: Q29

Original Answer Choice: [2] - The sled is at rest. **Incorrect**

Original Reasoning: I thought that the diagram was showing the velocity of the sled and that its velocity was equal to zero.

New Answer: [5] - The first three answers are all possible.

New Reasoning: All three answers are possible because the diagram is just showing that the force on the sled is constant and balanced.

Re: Dynamics Test: Q15-Q19

melissaberardi — Mon, 04 Jan 2010 00:17:46 -0000

Test Question: Q19

Original Answer Choice: [5] - The person exerts a force on the sled towards the left. The force is decreasing in strength. **Incorrect**

Original Reasoning: I thought that since the sled is moving to the left that there should be a force being exerted on the sled from the left. Also, I thought that since the sled was slowing down the force being exerted on the sled would decrease.

New Answer: [6] - The person exerts a force on the sled towards the left. The force is of constant strength (magnitude).

New Reasoning: I now understand that I was correct in which direction the force should be exerted on the sled so that it would move towards the left in this situation. This force should also be constant because the acceleration is constant, like in some of the other problems. I am now realizing that the forces should definitely be constant because since neither the acceleration or mass are changing, the net force would not change either. If the net force were to change in any of these constant acceleration problems, then the acceleration would not be constant anymore.

Re: Dynamics Test: Q15-Q19

melissaberardi — Mon, 04 Jan 2010 00:13:24 -0000

Test Question: Q18

Original Answer Choice: [7] - The person exerts a force on the sled towards the left. The force is increasing in strength (magnitude). **Incorrect**

Original Reasoning: I thought that there would have to be a force exerted from the left of the sled for it to move in that direction and that since the sled was "speeding up" at a constant acceleration, the strength of the force would also have to be increasing.

New Answer: [6] - The person exerts a force on the sled towards the left. The force is of constant strength (magnitude).

New Reasoning: I now understand that I was correct in which direction the force should be exerted, but since the acceleration is constant, the force the person exerts on the sled should also be constant.

Re: Dynamics Test: Q15-Q19

melissaberardi — Mon, 04 Jan 2010 00:09:30 -0000

Test Question: Q17

Original Answer Choice: [3] - The person exerts a force on the sled towards the right. The force is decreasing in strength (magnitude). **Incorrect**

Original Reasoning: I thought that since the sled is still moving to the right that there would need to be a force exerted from the right to be moving in that direction. Also, I thought that since the force is being slowed down at a constant acceleration that the force would have to be decreasing in strength.

New Answer: [2] - The person exerts a force on the sled towards the right. The force is of constant strength (magnitude).

New Reasoning: I now understand that I was correct in saying that there should be a force exerted from the right on the sled to have it move towards the right. However, the acceleration of the sled remains constant, which means that the force on the sled should also be of constant strength.