Work done by electrostatic force

[x86]

Homework Statement

A small, positively charged sphere is released from rest and moves directly away from a larger, positively charged sphere. During this process, the electrostatic force:

a) does positive work and increases the kinetic energy of the small sphere
b) does negative work and increases the kinetic energy of the small sphere

Homework Equations

The Attempt at a Solution

( + ) ----> (+)

So the electrostatic force is pushing the smaller charged force away. It looses potential energy and converts it into kinetic energy. Since W = (delta) (Kinetic energy) and kinetic energy increases, Ek > 0

Movement is also in the direction of the electric field (cos0) = 1 therefore it should be positive (as far as I know)

Work should be positive, the answer should be A)

However, the answer is B). Why?

It doesn't mathematically make sense to me. I've proven that W = change in kinetic energy.

However, when I conceptually think about it it makes sense that work is negative- because it's the same thing as a mass falling from a height- negative work is done on it.

Is this physics? Will it be full of exceptions and mathematical fallacies?

It seems like physics is turning more and more into a computer script

if case 1: do this algorithm
if case 2: do that algorithm

Is that it? Will I just have to just memorize these exceptions as I go along in physics, or is there another way of looking at it?

 

[Dick]

Homework Statement

A small, positively charged sphere is released from rest and moves directly away from a larger, positively charged sphere. During this process, the electrostatic force:

a) does positive work and increases the kinetic energy of the small sphere
b) does negative work and increases the kinetic energy of the small sphere

Homework Equations

The Attempt at a Solution

( + ) ----> (+)

So the electrostatic force is pushing the smaller charged force away. It looses potential energy and converts it into kinetic energy. Since W = (delta) (Kinetic energy) and kinetic energy increases, Ek > 0

Movement is also in the direction of the electric field (cos0) = 1 therefore it should be positive (as far as I know)

Work should be positive, the answer should be A)

However, the answer is B). Why?

It doesn't mathematically make sense to me. I've proven that W = change in kinetic energy.

However, when I conceptually think about it it makes sense that work is negative- because it's the same thing as a mass falling from a height- negative work is done on it.

Is this physics? Will it be full of exceptions and mathematical fallacies?

It seems like physics is turning more and more into a computer script

if case 1: do this algorithm
if case 2: do that algorithm

Is that it? Will I just have to just memorize these exceptions as I go along in physics, or is there another way of looking at it?

No, I think you have the right way of looking at it. The force does positive work on the kinetic energy of the system. I think it's more likely to be a typo in the answer than any need to reevaluate your basic concepts.

 

[x86]

No, I think you have the right way of looking at it. The force does positive work on the kinetic energy of the system. I think it's more likely to be a typo in the answer than any need to reevaluate your basic concepts.

Thank you for clearing my confusion