1- How can you measure the change in KE? 2- Wouldn't the change in KE always be the same? Each point is evenly spaced. 9- how would you find the magnitude of acceleration using the equation Ff=uN? 10- How would the length of the rod affect momentum?
Q1: what is the fundamental definition of work? W= fd cos(0)=delta KE Major mistake: people often mistake that this is true for any force. No work is done by a perpendicular force! Cos(90)=0 Negative work is when the force is in the opposite direction! Cos(180)=-1 So simply put if work is done thre must be a change in KE!
Q2- Same question as Aakash. The points were evenly spaced so I thought the change in KE would be the same as well. Q4-I understand now that even though the box was moving to the right that the only force acting on it was friction in the opposite direction. Q6- I don't understand why C is traveling faster than A when they hit the ground. If A falls straight down and C is projected horizontally, how does C pick up more speed than A? Q9- Wasn't sure how to find the acceleration of the box. - Domenic Bongiovanni
6) When I chose C I was thinking it has a centripetal force (probably not right) but also a speed increasing in the X and Y, so you need to find the total speed. Like finding the hypotenuse in a triangle.
2) The question asks which adjacent pairs have the greatest change in KE. Looking that this, I made up the number that each time it changes it goes down by a factor of 25%. So for all the adjacent pairs all the differences would be 25%. 3) The equation is (m)(1/r)^2 right? Or am I thinking this equation only applies to something else? 4) I accidentally chose the one for which way the box would move, not the forces applied to it. 5) I thought they should reach the bottom at the same time due to the fact that the question says the slope for B is frictionless. 9) Unsure
2) The ball would have the greatest difference in KE between points 1 and 2 because those are the points that have the greatest difference in the y direction. 3) What equation would be used here? 4) Is B because of friction in a centripetal circle. 5) Why doesn't C hit the ground last? 6) Why does C have the greatest speed?
2) I had the same thoughts as Aakash. 4) I had the correct answer and changed it, because I got confused in my head. I understand why it is correct because I initially had that answer. 7) I have no idea why I put D as my answer because I drew a picture and have the correct answer written right in front of my face on my drawing. I must have circled the wrong choice or something. 9) I am confused on how to relate static friction to kinetic friction. I know what they both are but I did not know how to solve it. 10) Again, I had the correct answer circled but changed it. I overthought it, but I understand now.
2. same thoughts as Aakash but I now understand 4. I over thought the question and confused myself but understand why the correct answer is B 10. I did the same as 4 and over thought because I was stuck between C and D -Jules Cino
Ok to all. When posting please see my example. Post the concept and idea that was the issue for your wrong answer that allowed you to see why your selection was incorrect. Example: #6 What is the formula for #6? THERE IS none it's an idea. It is a state function this is also related to number 1&2. The work or the change in PE is the agent of the change in KE. Because energy is conserved. By that reasoning they all have the same change in PE so will all have the same change in KE. So they all have the same velocity!!!!
Useful Skill: ignore the pathway the object takes to get there(the ramp/slope). If the pictures are the same then there is no difference.
1 - I don't understand why the object has to be on an angle in the picture? 2 - I thought the gretest change occurs at the bottom becasue of the backpack example. When a backpack swings in a circle, the strap will break at the bottom, therfore, wouldn't the greatest change occur at the bottom? 3 - I am confused as to how one would find the gravitational field using density and its radius. 7 - I completely forgot the idea behind mechanical energy. 9 - I have the same thoughts as Rachel. "I am confused on how to relate static friction to kinetic friction. I know what they both are but I did not know how to solve it. " 10 - I am confused as to where this equation is coming from? -Rayna Patel
2- There is the greatest change in height between 1 and 2. 3- What equation do we use for this? 6- Since c has an initial velocity greater than 0 also tie into why it hits the ground with the fastest speed? 9- Static friction vs. kinetic friction?? 10- I used p=mv and I understand that both masses have to be added together, buy why are we supposed to multiply them by the distance instead of the velocity?
2-I chose a because I thought since the only force acting upon the ball was gravity, which is constant, would keep the change constant for all, my second choice was c because Kinetic energy is dependent on velocity squared I thought the change involving the highest velocity would result in the biggest change. 4- I chose d because I knew there was a force of friction but I also thought there was another force pushing in the opposite direction because when you are in a care and it turns left you get pushed to the right 5- I chose d because I thought they all at the same starting velocity and acceleration but i didnt realize they have different distances to cover 6-I chose d because I thought all the blocks were traveling for the same amount of time with the same initial velocity and acceleration so they would have to have the same ending velocity 9-I got c because I used the F=ma formula and I solved for the mas and they gave you the force 10- I chose a because momentum is conserved so I thought the only momentum possibly allowed into the rod would be the momentum taken out of the ball.
2. My Answer D Explanation: I thought b/c they were same distance apart the change in KE was the same Answer A Explanation: While they are the same distance along the circular path, the greatest change in PE is between 1 & 2 because it loses the most height 3. My Answer A Explanation- No idea how to do it i completely guessed 5. My Answer D Explanation: I dont understand why my answer is wrong. All the blocks start on the same height, so the PE should change into the same amount of KE giving them the same amount of velocity and making them hit the ground at the same time 6. My Answer D Explanation: Same as above 9. My Answer B Explanation: No idea. Don't know the difference between static friction and kinetic friction or how to use them correctly in an equation 10. My Answer B Explanation: No idea
3. After looking at everything else, I think we need to look at this one. 4. Didn't realize it said only horizontal forces. 5. I believe that a and c are the same, as the v=0, and so the answer is b. 7. It gives you the answer, wow. 10.Wasn't sure if we added or subtracted, it makes sense now.
1- How can you measure the change in KE?
ReplyDelete2- Wouldn't the change in KE always be the same? Each point is evenly spaced.
9- how would you find the magnitude of acceleration using the equation Ff=uN?
10- How would the length of the rod affect momentum?
Q1: what is the fundamental definition of work? W= fd cos(0)=delta KE
ReplyDeleteMajor mistake: people often mistake that this is true for any force.
No work is done by a perpendicular force! Cos(90)=0
Negative work is when the force is in the opposite direction! Cos(180)=-1
So simply put if work is done thre must be a change in KE!
Follow up highly missed question.
DeleteHow much work is done by an 8N Fc for a 2 kg mass with a radius of 10m for 1 rotation?
Answer: 0 it follows the condition of a perpendicular force and can do no work. It only changes the direction of the velocity not the magnitude(speed)
Q2- Same question as Aakash. The points were evenly spaced so I thought the change in KE would be the same as well.
ReplyDeleteQ4-I understand now that even though the box was moving to the right that the only force acting on it was friction in the opposite direction.
Q6- I don't understand why C is traveling faster than A when they hit the ground. If A falls straight down and C is projected horizontally, how does C pick up more speed than A?
Q9- Wasn't sure how to find the acceleration of the box.
- Domenic Bongiovanni
6) When I chose C I was thinking it has a centripetal force (probably not right) but also a speed increasing in the X and Y, so you need to find the total speed. Like finding the hypotenuse in a triangle.
Delete2) The question asks which adjacent pairs have the greatest change in KE. Looking that this, I made up the number that each time it changes it goes down by a factor of 25%. So for all the adjacent pairs all the differences would be 25%.
ReplyDelete3) The equation is (m)(1/r)^2 right? Or am I thinking this equation only applies to something else?
4) I accidentally chose the one for which way the box would move, not the forces applied to it.
5) I thought they should reach the bottom at the same time due to the fact that the question says the slope for B is frictionless.
9) Unsure
-Matt Werman
2) The ball would have the greatest difference in KE between points 1 and 2 because those are the points that have the greatest difference in the y direction.
ReplyDelete3) What equation would be used here?
4) Is B because of friction in a centripetal circle.
5) Why doesn't C hit the ground last?
6) Why does C have the greatest speed?
- Chris Rha
2) I had the same thoughts as Aakash.
ReplyDelete4) I had the correct answer and changed it, because I got confused in my head. I understand why it is correct because I initially had that answer.
7) I have no idea why I put D as my answer because I drew a picture and have the correct answer written right in front of my face on my drawing. I must have circled the wrong choice or something.
9) I am confused on how to relate static friction to kinetic friction. I know what they both are but I did not know how to solve it.
10) Again, I had the correct answer circled but changed it. I overthought it, but I understand now.
2. same thoughts as Aakash but I now understand
ReplyDelete4. I over thought the question and confused myself but understand why the correct answer is B
10. I did the same as 4 and over thought because I was stuck between C and D
-Jules Cino
This comment has been removed by the author.
DeleteOk to all.
ReplyDeleteWhen posting please see my example.
Post the concept and idea that was the issue for your wrong answer that allowed you to see why your selection was incorrect.
Example: #6
What is the formula for #6?
THERE IS none it's an idea.
It is a state function this is also related to number 1&2. The work or the change in PE is the agent of the change in KE. Because energy is conserved. By that reasoning they all have the same change in PE so will all have the same change in KE. So they all have the same velocity!!!!
Useful Skill: ignore the pathway the object takes to get there(the ramp/slope). If the pictures are the same then there is no difference.
Issues: works well for friction less ramps!
1 - I don't understand why the object has to be on an angle in the picture?
ReplyDelete2 - I thought the gretest change occurs at the bottom becasue of the backpack example. When a backpack swings in a circle, the strap will break at the bottom, therfore, wouldn't the greatest change occur at the bottom?
3 - I am confused as to how one would find the gravitational field using density and its radius.
7 - I completely forgot the idea behind mechanical energy.
9 - I have the same thoughts as Rachel. "I am confused on how to relate static friction to kinetic friction. I know what they both are but I did not know how to solve it. "
10 - I am confused as to where this equation is coming from?
-Rayna Patel
2- There is the greatest change in height between 1 and 2.
ReplyDelete3- What equation do we use for this?
6- Since c has an initial velocity greater than 0 also tie into why it hits the ground with the fastest speed?
9- Static friction vs. kinetic friction??
10- I used p=mv and I understand that both masses have to be added together, buy why are we supposed to multiply them by the distance instead of the velocity?
2-I chose a because I thought since the only force acting upon the ball was gravity, which is constant, would keep the change constant for all, my second choice was c because Kinetic energy is dependent on velocity squared I thought the change involving the highest velocity would result in the biggest change.
ReplyDelete4- I chose d because I knew there was a force of friction but I also thought there was another force pushing in the opposite direction because when you are in a care and it turns left you get pushed to the right
5- I chose d because I thought they all at the same starting velocity and acceleration but i didnt realize they have different distances to cover
6-I chose d because I thought all the blocks were traveling for the same amount of time with the same initial velocity and acceleration so they would have to have the same ending velocity
9-I got c because I used the F=ma formula and I solved for the mas and they gave you the force
10- I chose a because momentum is conserved so I thought the only momentum possibly allowed into the rod would be the momentum taken out of the ball.
2.
ReplyDeleteMy Answer D Explanation: I thought b/c they were same distance apart the change in KE was the same
Answer A Explanation: While they are the same distance along the circular path, the greatest change in PE is between 1 & 2 because it loses the most height
3.
My Answer A Explanation- No idea how to do it i completely guessed
5.
My Answer D Explanation: I dont understand why my answer is wrong. All the blocks start on the same height, so the PE should change into the same amount of KE giving them the same amount of velocity and making them hit the ground at the same time
6.
My Answer D Explanation: Same as above
9.
My Answer B Explanation: No idea. Don't know the difference between static friction and kinetic friction or how to use them correctly in an equation
10.
My Answer B Explanation: No idea
3. After looking at everything else, I think we need to look at this one.
ReplyDelete4. Didn't realize it said only horizontal forces.
5. I believe that a and c are the same, as the v=0, and so the answer is b.
7. It gives you the answer, wow.
10.Wasn't sure if we added or subtracted, it makes sense now.