Physics: Post your doubts here!

[Unicorn]

What is the relationship between potential energy and electric field force? the equation is f= dU/dx where U is potential energy but what is x??

 

[confused123]

Its nice to see that students of physics are very conscious to clear their concepts. I am expecting the same behavior from the students of A level ECONOMICS. If any of you is taking economics <Content Removed>

let them advertise what they want. what's wrong in it? this is a open forum for all i think as long as they are not spamming or abusing then let teachers help students by promoting themselves.

 

[confused123]

What is the relationship between potential energy and electric field force? the equation is f= dU/dx where U is potential energy but what is x??

does this come under as physics syllabus? :/

 

[Unicorn]

let them advertise what they want. what's wrong in it? this is a open forum for all i think as long as they are not spamming or abusing then let teachers help students by promoting themselves.

help students or themselves? and besides this is a physics forum not economics

 

[Unicorn]

does this come under as physics syllabus? :/

apparently yes. It is from the notes on the first page of this thread

it is on page 17

 

[confused123]

help students or themselves? and besides this is a physics forum not economics

its always mutual benefit. grow up dude. yeah the teacher didn't knew the correct section in the forum to write that..

 

[Unicorn]

its always mutual benefit. grow up dude. yeah the teacher didn't knew the correct section in the forum to write that..

umm honey he said it is great to see physics students studying hard for their subject -_-

anyways lets just forget this

 

[confused123]

umm honey he said it is great to see physics students studying hard for their subject -_-

anyways lets just forget this

yeah but if you see other forums there are sections for teachers to advertise and anyone can offer teaching. ok lets 4get it. going off topic

r u sure that electric field and potential energy question is in the syllabus? can you check syllabus.

 

[Unicorn]

yeah but if you see other forums there are sections for teachers to advertise and anyone can offer teaching. ok lets 4get it. going off topic

r u sure that electric field and potential energy question is in the syllabus? can you check syllabus.

just did and yes it is except they don't have this weird equation

 

[NokiaN95638]

Guys help me with this question:
http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s04_qp_2.pdf

Q no. 1b

 

[DragonCub]

What is the relationship between potential energy and electric field force? the equation is f= dU/dx where U is potential energy but what is x??

x = distance from the centre.
Work done is equal to force × distance, this is the formula.
In fact, when force changes with distance (a function of distance), the work should be calculated by integrating force × dx. On a force-against-distance diagram, the area under the line/curve is work done.
Usually, force is constant no matter how distance changes, the graph is then a horizontal line. That's why the formula W = Fx comes from.

 

[DragonCub]

Guys help me with this question:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s04_qp_2.pdf

Q no. 1b

The diagram can be drawn using the Parallelogram Rule.

To find the resultant magnitude, there are two ways:
- you have a rule don't you? Use it to measure the relative length of the forces. Force magnitude ratio equals diagram length ratio. Use the ratio to calculate. This is the "unprofessional" way but it works.
- use purely mathematics to calculate the force. Resolve the two forces and you get for the 6N, x-component is 6 cos40, y-component 6 sin40. The 8N, x-component 8, y-component 0. So the resultant x-component = 8 + 6 cos40, y-component 6 sin40.
Resultant magnitude, using Pythagorean Theorem, is sqrt [(8 + 6 cos40)^2 + (6 sin40)^2].
Answer should be 13.2N.

 

[Unicorn]

x = distance from the centre.
Work done is equal to force × distance, this is the formula.
In fact, when force changes with distance (a function of distance), the work should be calculated by integrating force × dx. On a force-against-distance diagram, the area under the line/curve is work done.
Usually, force is constant no matter how distance changes, the graph is then a horizontal line. That's why the formula W = Fx comes from.

i didn't really get that. I know that W= F x s

but the equation said dU/dx where is U is potential energy where is x in potential energy to be differentiated??

 

[DragonCub]

i didn't really get that. I know that W= F x s

but the equation said dU/dx where is U is potential energy where is x in potential energy to be differentiated??

It is not x to be differentiated but Ep (potential energy) to be, with respect to x.
Think about the relationship between velocity and displacement. Velocity is defined as the rate (rapidness) of change of displacement, or dx/dt. Here the rate of change is in terms of time. So it's dx/dt
Likewise, force is an indicator of how rapidly work done responds to changes in distance. The rapidness is in terms of distance, so it's dW by dx.

 

[Soulgamer]

Help in question number Question.5 (C) (i) (ii)

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_21.pdf


M.S
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_ms_21.pdf

Please explain in a bit detail and not just an answer which is the exact replica of the marking scheme.
Please and Thankyou!

 

[DragonCub]

Help in question number Question.5 (C) (i) (ii)

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_21.pdf


M.S
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_ms_21.pdf

Please explain in a bit detail and not just an answer which is the exact replica of the marking scheme.
Please and Thankyou!

(1)Electric field lines point from positive side towards negative side, so P experiences a rightward force while N a leftward force.

(2)Torque is a kind of moment. It is the moment of a couple.
Here the forces on two charges form a perfect couple.
The formula for torque (T): T = F d [d = vertical distance between the forces]
Use charge and electric field strength to calculate F:
F = 1.6E^-19 × 5.0E^4 = 8.0E^-15 N
Use the length PN and sine of the angle to calculate d:
d = 2.8E^-10 × sin30 =1.4E^-10 m
Last, calculate the torque:
T = 8.0E^-15 × 1.4 E^-10 = 1.12E^-24 N m

 

[Unicorn]

It is not x to be differentiated but Ep (potential energy) to be, with respect to x.
Think about the relationship between velocity and displacement. Velocity is defined as the rate (rapidness) of change of displacement, or dx/dt. Here the rate of change is in terms of time. So it's dx/dt
Likewise, force is an indicator of how rapidly work done responds to changes in distance. The rapidness is in terms of distance, so it's dW by dx.

Ohhhh Thanks a lot ♥

 

[DragonCub]

Ohhhh Thanks a lot ♥

My pleasure. That is indeed a question with depth.

 

[Soulgamer]

(1)Electric field lines point from positive side towards negative side, so P experiences a rightward force while N a leftward force.
View attachment 10316
(2)Torque is a kind of moment. It is the moment of a couple.
Here the forces on two charges form a perfect couple.
The formula for torque (T): T = F d [d = vertical distance between the forces]
Use charge and electric field strength to calculate F:
F = 1.6E^-19 × 5.0E^4 = 8.0E^-15 N
Use the length PN and sine of the angle to calculate d:
d = 2.8E^-10 × sin30 =1.4E^-10 m
Last, calculate the torque:
T = 8.0E^-15 × 1.4 E^-10 = 1.12E^-24 N m

Thank you so much!

 

[A.ELWY 7]

yes i found that this F= -(dU/dx) is in the syllabus but i didnt understand it...what is the d and x