Question

a positive test charge q is released near a positive fixed charge Q. As q moves away from Q, it will move with
a) increasing a
b) constant v
c) constant a
d) decreasing a

Answer 1

i wanted to say b but if a=F/m, F_e gets smaller as r increases...so it will move with a...not constant a since the value of a changes as F changes...?

Answer 2

As the test charge q moves away from Q, the force on q diminishes by Coulomb's law as 1/r^2. Therefore the acceleration on q also diminishes.

Given that, what's the answer?

Answer 3

constant v

Answer 4

There's still a force acting on the test charge, so it must be accelerating. And hence velocity cannot be constant, by Newton's First Law.

Answer 5

o, decreasing?

Answer 6

The force is decreasing, hence the acceleration is decreasing.

Answer 7

Therefore the answer is
d) decreasing a

Answer 8

ok, i get hung up words. so a is going to 0?

Answer 9

Yes, force is decreasing and as time --> infinity, Force --> 0.

Therefore as t --> infinity, acceleration --> 0.

Answer 10

ok thx