Grade 11 Physics Help: Solving 3 Challenging Questions for Your Exam Tomorrow

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In summary: I think I got the answer to this one by using e=mgh and e=1/2mv^2. So thanks!3) I am not sure about all this. All I have is a diagram that shows an electron heading downwards, and the question "Describe the Path of the electron beam as it passed by the south pole".Also, I got another question that is :confused: me.4)A box with an inital speed of 2m/s slides to a rest on a horizontal floor in 3 metres. What is the coefficient of kinetic friction?What I have done
  • #1
leafs rule
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Hi guys. First time posting, and I really need some help on some physics questions. We received some review of about 40 questions for our exam(tomorrow!), and these 3 have stumped me.

1) If there are two points on a conductor each with the same potential...what is the signifigance of these two points? And how much work would be required to move a charge between these two points?

2) A roller coaster reaches the top of a grade at 10 m/s. It then goes downhill and uphill once more. If the second peak is 15m lower than the first, how fast will the roller cosaster be moving at that peak(neglecting friction)?

3) If an electrion moving downards past a magnet's south pole, what will be the electron beam's path as it mvoes by the south pole?

Help would be appericatd. Thanks.
 
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  • #2
leafs rule said:
Hi guys. First time posting, and I really need some help on some physics questions. We received some review of about 40 questions for our exam(tomorrow!), and these 3 have stumped me.

1) If there are two points on a conductor each with the same potential...what is the signifigance of these two points? And how much work would be required to move a charge between these two points?
look up the definition of potential, and how its related to work.

2) A roller coaster reaches the top of a grade at 10 m/s. It then goes downhill and uphill once more. If the second peak is 15m lower than the first, how fast will the roller cosaster be moving at that peak(neglecting friction)?
This is definately a conservation of energy problem,, show what you've done so far, no one will do the work for you.

3) If an electrion moving downards past a magnet's south pole, what will be the electron beam's path as it mvoes by the south pole?
Which way does the magnetic field point near the south pole.
What will be the force on the electron as a result of this magnetic field
( The equation involves cross products )
 
  • #3
Concerning 2), you will need the mass of the roller coaster.
 
  • #4
MathStudent said:
1)look up the definition of potential, and how its related to work.


2)This is definately a conservation of energy problem,, show what you've done so far, no one will do the work for you.


3)Which way does the magnetic field point near the south pole.
What will be the force on the electron as a result of this magnetic field
( The equation involves cross products )

1) Potential is the amount of potential energy per coloumb. 1 joule of energy is required to move one coulomb of charge through an electric field. Would that be the answer they are looking for? Also, what do they mean by "discuss the signifigance of these two points"? Would these two points be the poles or something?

2) I think I got the answer to this one by using e=mgh and e=1/2mv^2. So thanks!

3) I am not sure about all this. All I have is a diagram that shows an electron heading downwards, and the question "Describe the Path of the electron beam as it passed by the south pole".

Also, I got another question that is :confused: me.

4)A box with an inital speed of 2m/s slides to a rest on a horizontal floor in 3 metres. What is the coefficient of kinetic friction?

What I have done: found time.
d=[(vi + v2)/2](t)
3=(2/2)(t)
t=3s

Found acceleration
to be
2/3 m/s^2

But i have no idea where to go now. I don't know how to find friction coefficients without being given any forces!
 

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  • #5
Also, a 5th question. I thought I could figure out this question, but I cant!

A stone is dropped into a well. The sound of the splash is hear 3s after the stone is dropped. What is the depth of the well.

For some reason, the q doesn't give me a temperature to figure out the speed of sound.. so i just assumed it was 0 degrees celsius.

What I did was: I used sound equations and kinematic equations.
Vs=332 m/s
I knew that the time it took for the stone to hit the water and for a sound to come back would be 3 seconds. So t1(time for it to hit water) + t2(time it took for sound to come up)=3s
t1+t2=3s

d=v1*t1 + 1/2*9.81*t1^2
d=4.905*t^2
(d/4.905)^1/2=t1

d=Vs*t2
d/332=t2

so...t1+t2=3=(d/332) + [(d/4.905)^1/2]

I do all that, and eventually come to a quadratic equation. And then it just gets really complex, and I get a completley wrong answer(like 870000 m). What am I doing wrong?
 
  • #6
leafs rule said:
1) Potential is the amount of potential energy per coloumb. 1 joule of energy is required to move one coulomb of charge through an electric field. Would that be the answer they are looking for?
What I was hoping you would recognize (and maybe your book doesn't mention this ) is that Work is equal to the change in potential energy, that is

[tex] \vert \abs{W} \vert = \vert \Delta U \vert \ \ \ \ \ \ \ \ (1)[/tex]

as you mentioned potential is the potential energy of a unit charge, therefore

[tex] V = \frac{U}{q} [/tex]

[tex]\Rightarrow \Delta V = \frac{ \Delta U }{q} [/tex]

if we divide (1) by q, then

[tex] \vert \abs{ \frac{W}{q} } \vert = \vert \frac{\Delta U}{q} \vert [/tex]

[tex]\Rightarrow \vert \frac{W}{q} \vert = \vert \Delta V \vert [/tex]

Thus [itex] \Delta V [/itex] can be thought of the work done on a unit charge by an electric field.


Also, what do they mean by "discuss the signifigance of these two points"? Would these two points be the poles or something?
I think figuring out the second part of the problem first will help you with this question.


3) I am not sure about all this. All I have is a diagram that shows an electron heading downwards, and the question "Describe the Path of the electron beam as it passed by the south pole".
By convention, the magnetic field [itex] \vec{B} [/itex] points toward the south end of a magnet.
In order for the electron to change its path, it needs to have an acceleration, so by Newton's second law it needs to have a force acting on it.
What is the equation of the force acting on a point charge by a magnetic field?, Its

[tex] \vec{F} = q \vec{v} \ X \ \vec{B} [/tex]

So if you can find the direction of the force, you know the direction of acceleration, and thus the change in the direction of the e's velocity. (Do you know how to find the direction of a cross product? )


Also, I got another question that is :confused: me.

4)A box with an inital speed of 2m/s slides to a rest on a horizontal floor in 3 metres. What is the coefficient of kinetic friction?

What I have done: found time.
d=[(vi + v2)/2](t)
3=(2/2)(t)
t=3s

Found acceleration
to be
2/3 m/s^2

But i have no idea where to go now. I don't know how to find friction coefficients without being given any forces!
Be careful about signs, the equation for acceleration is

[tex] a = \frac{v_f - v_i}{t} [/tex]

[tex]\Rightarrow a = \frac{ 0 - 2 }{3}[/tex]

[tex]\Rightarrow a = - \frac{2}{3} \frac{m}{s^2} [/tex]

Set up a Free-Body-Diagram for the box.
Then set up Newtons second law equations for the vertical and horizontal components of force.
You have the horizontal component of acceleration so see if you can solve what the force of fricion is... then you can use the uquation for friction to find the coefficient.
 
  • #7
MathStudent said:
What I was hoping you would recognize (and maybe your book doesn't mention this ) is that Work is equal to the change in potential energy, that is

[tex] \vert \abs{W} \vert = \vert \Delta U \vert \ \ \ \ \ \ \ \ (1)[/tex]

as you mentioned potential is the potential energy of a unit charge, therefore

[tex] V = \frac{U}{q} [/tex]

[tex]\Rightarrow \Delta V = \frac{ \Delta U }{q} [/tex]

if we divide (1) by q, then

[tex] \vert \abs{ \frac{W}{q} } \vert = \vert \frac{\Delta U}{q} \vert [/tex]

[tex]\Rightarrow \vert \frac{W}{q} \vert = \vert \Delta V \vert [/tex]

Thus [itex] \Delta V [/itex] can be thought of the work done on a unit charge by an electric field.



I think figuring out the second part of the problem first will help you with this question.



By convention, the magnetic field [itex] \vec{B} [/itex] points toward the south end of a magnet.
In order for the electron to change its path, it needs to have an acceleration, so by Newton's second law it needs to have a force acting on it.
What is the equation of the force acting on a point charge by a magnetic field?, Its

[tex] \vec{F} = q \vec{v} \ X \ \vec{B} [/tex]

So if you can find the direction of the force, you know the direction of acceleration, and thus the change in the direction of the e's velocity. (Do you know how to find the direction of a cross product? )



Be careful about signs, the equation for acceleration is

[tex] a = \frac{v_f - v_i}{t} [/tex]

[tex]\Rightarrow a = \frac{ 0 - 2 }{3}[/tex]

[tex]\Rightarrow a = - \frac{2}{3} \frac{m}{s^2} [/tex]

Set up a Free-Body-Diagram for the box.
Then set up Newtons second law equations for the vertical and horizontal components of force.
You have the horizontal component of acceleration so see if you can solve what the force of fricion is... then you can use the uquation for friction to find the coefficient.



I had trouble understanding questions 2 and 3, but thankfully nothing on them was on the exam! Right now I have to study for my math exam, but I'll be sure to read over your post again once I am done that(for next year)! Thanks man!
 
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1. What are the main topics covered in Grade 11 Physics?

Grade 11 Physics typically covers topics such as motion, forces, energy, electricity, and waves. It also introduces students to key concepts like vectors, Newton's laws of motion, and basic thermodynamics.

2. What are some resources for getting help with Grade 11 Physics?

There are many resources available for students who need help with Grade 11 Physics. Some options include online tutorials, study guides, practice problems, and peer tutoring. Your teacher or school may also have additional resources or offer extra help sessions.

3. How can I improve my understanding of Physics concepts?

To improve your understanding of Physics concepts, it's important to practice solving problems and to review your notes and textbook regularly. You can also try teaching the concepts to someone else, as this can help solidify your understanding. Additionally, seeking help from a teacher or tutor can also be beneficial.

4. What are some common mistakes students make in Grade 11 Physics?

Some common mistakes students make in Grade 11 Physics include not fully understanding the basic concepts, not showing all the steps in problem solving, and not practicing enough. It's also important to pay attention to units and to use the correct formulas and equations.

5. How can I prepare for exams in Grade 11 Physics?

To prepare for exams in Grade 11 Physics, it's important to review your notes, textbooks, and practice problems. You can also create study guides or flashcards to help you remember key concepts and formulas. Additionally, make sure to get enough rest and eat well before the exam to ensure your brain is functioning at its best.

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