Need Help with Physics

[Masroor Hussain]

Need Help Physics:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w10_qp_32.pdf
I'm getting the wrong answer for question 2(b)(ii). I Think the height is 0.2 m but the ms say's it's 0.1, why is it 0.1 m not 0.2.

 

[igcsephysicstutor]

the gpe of the bob is 0.45J at the start (height above ground is 0.3m). at its lowest position, its height is 0.2m above the ground, so is gpe is 0.3J, meaning that is k.e. must be 0.15J (0.45-0.30).

so, 0.15J = half mass x speed squared = 0.5 x 0.15 x v^2

this give v^2 = 2, so v = sqrt(2) = 1.4

 

[Masroor Hussain]

the gpe of the bob is 0.45J at the start (height above ground is 0.3m). at its lowest position, its height is 0.2m above the ground, so is gpe is 0.3J, meaning that is k.e. must be 0.15J (0.45-0.30).

so, 0.15J = half mass x speed squared = 0.5 x 0.15 x v^2

this give v^2 = 2, so v = sqrt(2) = 1.4

Thanks!