Trial paper problem (1 Viewer)

[mathsbrain]

Hi all,

I am studying for my trials and i found these two questions to be unbelievably hard, can someone please lend a helping hand.

In the kings 2007 trial:

Q5a) I get a "plus" between the RHS terms rather than "minus". Can someone please explain with solutions?

Q6a) (i) i had no idea....even though its only 1 mark.

In the Ruse Trial(note i have uploaded the trial solution as well):

part c) (ii) in their solution, if you read their 2nd line of working for c(ii), they substituted v=1/2v only in one of the v's, but sin and cos both are in terms of v, shouldnt they be substituted as 1/2v as well?

 

[rolpsy]

okay here's 5(a)
Resolving forces along the bank can be tricky. If all else fails, resolve horizontally and vertically, then solve simultaneously.

 

[mathsbrain]

okay here's 5(a)
Resolving forces along the bank can be tricky. If all else fails, resolve horizontally and vertically, then solve simultaneously.

Hi THanks for your help, but here is my working, can you please find out what is wrong?

 

[mathsbrain]

okay here's 5(a)
Resolving forces along the bank can be tricky. If all else fails, resolve horizontally and vertically, then solve simultaneously.

Hi Frank,

I think in your solution you've assumed the car is falling downwards along the line BA, hence you claim resultant force is (mv^2/r) *cos(theta), but i think the resultant force along BA should be 0 as the car should not be sliding up or down

 

[rolpsy]

remember that mv²/r is the resultant force (horizontally); the other forces must add to give this.
the same principle applies when you resolve this resultant force into its components.

to convince yourself, resolve horizontally and vertically, then solve simultaneously (times vertical by sin, horizontal by cos, then subtract)


and lol my name isn't frank... that's the first word that popped into my head

 

[mathsbrain]

Right, thanks my rolpsy!

Please help with the rest!!! haha

 

[mathsbrain]

Can someone please help? Carrotstick? Deswa? Sean? Math man?

 

[math man]

6 a (i) is fairly easy.
Just use ratio intercept thm since AQ is parallel to SD which gives (PS)/(QD)=(PS)/(AS), but
you are given (PD)/(QD)=(PS)/(QS), equating the two gives AS=QS.

Ill look at reast now

 

[math man]

 

[math man]

the question is stupid to use v and not v_0 or some other distinguishable variable for optimal speed in (i), which is what confused you

 

[mathsbrain]

the question is stupid to use v and not v_0 or some other distinguishable variable for optimal speed in (i), which is what confused you

thx!!!