MYTUTOR SUBJECT ANSWERS

139 views

Two electrons are a distance r apart, the first electron exerts a force F on the second electron. a) What force does the second electron exert on the first? b) In terms of r, at what distance is the force that the first electron exerts on the second F/9?

This question is on electric forces between charged particles. A useful equation to consider is Coulomb's law:

F=k(Q1Q2)/R2

Where k is the Coulomb's law constant:

k~9.0x109Nm2/C2

Q is the charge on each particle in Coulombs, R is the distance in metres and F is the force in Newtons.

a) This part is a simple application of Newton's third law, as the first electron is exerting a repulsive force F on the second, the second must also be exerting a repulsive force F on the first. (Every force has an equal and opposite reaction force!)

b) This section requires you to look at Coulomb's law. It is what is known as an inverse square law, this effectively means the force decreases proportionally to the square of the distance, so for the force to have decreased by a factor of 9, the distance must have increased by a factor of the square root of nine, this equals 3, so the new distance is 3r. Nothing else in the equation changes, so they all other terms can be treated as constants and ignored.

This can be seen more explicitly by mathematically manipulating Coulomb's law, however I find it easier and more useful to instead find the answer by just thinking about the underlying link between force and distance in this equation, this means you develop a proper understanding of the inverse square relationship.

Ross W. GCSE Physics tutor, A Level Physics tutor, GCSE Maths tutor, ...

4 months ago

Answered by Ross, an A Level Physics tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist

47 SUBJECT SPECIALISTS

£22 /hr

Samuel H.

Degree: Mathematics with International Study (Masters) - Exeter University

Subjects offered: Physics, Maths

Physics
Maths

“I have not only been able to teach AS Level students how to solve mechanics problems; I helped them understand the concepts behind the problems”

£20 /hr

Matthew H.

Degree: Physics (Masters) - Liverpool University

Subjects offered: Physics, Maths+ 3 more

Physics
Maths
History
Chemistry
-Personal Statements-

“About Me  I am studying physics at the University of Liverpool and am now in my second year having passed with a first in all my modules last year. I really love all things science and have a real drive to pass on what I know to other...”

£20 /hr

Raghav A.

Degree: Chemical Engineering (Masters) - Bath University

Subjects offered: Physics, Maths+ 2 more

Physics
Maths
Chemistry
-Personal Statements-

“About Me I am currently studying Chemical Engineering at the University of Bath. I have always had a real passion for mathematics and science and hope that my tutorials will instill that in you, too. I am very patient and friendly. I...”

MyTutor guarantee

About the author

Ross W.

Currently unavailable: for regular students

Degree: MPhys (Masters) - Durham University

Subjects offered: Physics, Maths+ 4 more

Physics
Maths
Further Mathematics
Chemistry
Biology
-Personal Statements-

“I am a second year student studying Physics at Durham University (very pleased with my first year results - got a 1st - yay!) I have always been fascinated by science and maths and their ability to explain the world around us. What Do...”

MyTutor guarantee

You may also like...

Posts by Ross

A rollercoaster carriage of mass 100kg has 45kJ of Kinetic Energy at the lowest point of its ride. Ignoring air resistance and friction between the wheels and the tracks, what is the maximum height above this point it could reach? [Take g as 10m/s/s)

Two electrons are a distance r apart, the first electron exerts a force F on the second electron. a) What force does the second electron exert on the first? b) In terms of r, at what distance is the force that the first electron exerts on the second F/9?

Other A Level Physics questions

If the highest frequency a song is 10 kHz and it is encoded at 16 bits per sample what is the minimum number of bytes needed to encode the 3 minute song?

Why does a single slit diffraction pattern occur?

Derive I = nAVe

What is "half-life"?

View A Level Physics tutors

Cookies:

We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok