MHB What is the Velocity of a Released Point Charge in Physics?

  • Thread starter Thread starter ISITIEIW
  • Start date Start date
  • Tags Tags
    Charge Physics
AI Thread Summary
A point charge q2 is released from rest 1 meter away from a fixed charge q1 and is questioned about its velocity when it reaches 7 meters from q1. The calculated answer is 0.0255 m/s, but the user struggles with the method. The issue lies in using a kinematic equation that assumes constant acceleration, which is not applicable here due to the changing force between the charges. Instead, integrating the acceleration or applying the Conservation of Energy principle is recommended for accurate results. Understanding these concepts is crucial for solving problems involving point charges in physics.
ISITIEIW
Messages
17
Reaction score
0
Hey guys, I didn't know where i could post this problem, but you guys seemed the best for the job :p

A point charge q1=+120nC, is fixed in space and can not move. A second point charge, q2=+6nC, is initially held at rest 1 m away from charge q1. Charge q2, is then released from rest. How fast will charge q2 be moving when it is 7m away from charge q1? The mass of q2 is 17g and you may ignore the effects of gravity.

Alright so the answer is 0.0255 m/s, but i can never get this,

I did that the sum of the forces in the x direction are, k being 8.85e-12, r being 1m , and m being 0.017kg (kq1q2)/(r)^2=ma

I can solve for a then substitute this into the kinematic equation vf^2 = vi^2 +2ad
where vi would be 0, and solve for vf, and d would be 6 m. But does not give the correct answer.

What am i doing wrong ?? Please help
Thanks a lot!

ISITIEIW
 
Mathematics news on Phys.org
The kinematics equation you are using to find the final velocity applies to constant acceleration only. You are going to need to integrate due to the changing acceleration with respect to position.
 
Or it might be easier to use Conservation of Energy.
 
Seemingly by some mathematical coincidence, a hexagon of sides 2,2,7,7, 11, and 11 can be inscribed in a circle of radius 7. The other day I saw a math problem on line, which they said came from a Polish Olympiad, where you compute the length x of the 3rd side which is the same as the radius, so that the sides of length 2,x, and 11 are inscribed on the arc of a semi-circle. The law of cosines applied twice gives the answer for x of exactly 7, but the arithmetic is so complex that the...
Is it possible to arrange six pencils such that each one touches the other five? If so, how? This is an adaption of a Martin Gardner puzzle only I changed it from cigarettes to pencils and left out the clues because PF folks don’t need clues. From the book “My Best Mathematical and Logic Puzzles”. Dover, 1994.
Thread 'Imaginary Pythagoras'
I posted this in the Lame Math thread, but it's got me thinking. Is there any validity to this? Or is it really just a mathematical trick? Naively, I see that i2 + plus 12 does equal zero2. But does this have a meaning? I know one can treat the imaginary number line as just another axis like the reals, but does that mean this does represent a triangle in the complex plane with a hypotenuse of length zero? Ibix offered a rendering of the diagram using what I assume is matrix* notation...
Back
Top