Help mechanics paper 4 :(

[waleedsmz]

http://www.xtremepapers.me/CIE/Internat ... _qp_41.pdf

This exam question number 6) ii) Vg: Vb
the mark scheme relates the height to the velocity? I don't really get that. Please help...

Link to mark scheme: http://www.xtremepapers.me/CIE/Internat ... _ms_41.pdf

 

[ahmed t]

just find the velocity at B which will
1.6=0.5mv^2
v will be 4

now G loss in pe is 3*10*0.2=6
so loss in pe is gain in pe
6=0.5mV^2
find this v it shud be 2square root 15
now divide vg/vb
it will guve u 1.94
simple

 

[waleedsmz]

Thank you so much but this wasn't the question I asked

I was aiming for ii)

 

[ahmed t]

oh sorry
see this is wat u do
u find the Vg and Vb in terms of H
Vg is going to be
mgh=0.5mv^2
so we
here h is H
so we go like this
20H is Vg^2

now Vb
mgh=0.5mv^2
here h is (H-2.2)
so 20(H-2.2) is Vb^2
so Vg/Vb
so that will be
square root 20H/square root 20(H-2.2) =2.55
square both sides giving u
20H/20(H-2.2)=2.55^2
cancel out the 20's and find H

 

[waleedsmz]

Seriously should someone be able to know that in a freakin exam?!
Thanks so much anyways You really helped me