Question

A pendulum is swinging from A to B then to C and goes back to A . Calculate its maximum speed at C . See the attachement

Answer 1

are you doing this symbolically or with actual numbers?

Answer 2

You can see that at A and B the mass is slightly higher than it is at C. You can calculate how much higher using trigonometry. (Start by drawing a horizontal line between A and B - look for right angle triangles....)
So - the mass is a distance h above C - and it's velocity is 0.
Its PE (relative to C) is mgh
When it is at C ALL that PE has been converted to KE (= m*(v^2)/2 )

so you know that KE = PE
mgh = m *(v^2)/2

You know g and h , m cancels out, so calculate v

Answer 3

@roadjester actual numbers :)