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## Homework Statement

a - ##\vec F = \vec F_0 \sin(at) ##

b - ##F = A\theta \hat r##, A constant and ## 0 \le \theta < 2\pi ##. ##\vec F## is limited to the (x,y) plane

c - A force which depends on the velociity of a particle but which is always perpendicular to the velocity

## Homework Equations

## The Attempt at a Solution

I don't know what to say for (a)

a -

b - Not conservative because ##\vec \nabla \times \vec F = -\frac{A}{r} \hat k \neq \vec 0 ##

c - Conservative because instantaneous work is 0, so the work done on any closed path is 0 : ##\vec F.d\vec r = \vec F.\vec v\ dt = 0 ##