M3: vertical circles

in c: why in the mark scheme are they working out the horizontal velocity when working out the max height?

Are you sure they have?

Which year is the question from?

yes.

I see. I didn't do it like that!

The horizontal component of the velocity doesn't change, so the speed at the top of the motion is just the horizontal component.

They've then used conservation of energy from B to the top to find h.

Personally i found sin(180- theta) and used that to find the vertical component at B. Then suvat to find h.

I would do it the same (vertical velocity) but why 180 - theta?

At B cos theta is negative, so theta is obtuse. It is easier to work with an acute angle, hence 180 - theta.

I'll draw up a diagram and get back to you in about 10 minutes

I see. I didn't do it like that!

The horizontal component of the velocity doesn't change, so the speed at the top of the motion is just the horizontal component.

They've then used conservation of energy from B to the top to find h.

Personally i found sin(180- theta) and used that to find the vertical component at B. Then suvat to find h.

The Jan 2012 mark scheme does also offer my method and a third one.