Mechanics doubts Paper 4

[1992]

hello
can someone solve me this 2 small questions from M/J 2007
its Q 1. ii) and Q 2. i) ii)
With explantion please or steps needed. the mark sscheme doesnt explain it well

 

[intel1993]

K.E= 1/2 m (1.5^2 - 2.5^2)
k.e= 2m..... ignore minus sign here as it is energy....but decceleration is occuring that why minus sign....

W.d = f into d....
2m/4 = f
1/2 m= f

f=ma
1/2m=ma
a= 1/2...


ma= mg sin alpha as it is smooth plane so no friction exist and no extrenal force is there thats why this equation applies....

a= g sin alpha

now put values to calculate alpha...................

 

[intel1993]

Q2 i) as component of resultant given ( magnitude is not given only horizontal companonet of resultant) so......

8 + 8 cos @ = 9
solve it for @

@=82.8...

ii) horizontal component= 8 + 8cos 82.8
vertical component = 8 sin 82.8
now solve it for thsi equation...
horizontal component ^2 + vertical componet ^2= resultant ^2

u will get ur ans....

 

[1992]

thanks