Question Number
Scheme
Marks
2. (a)
Mass ratio
4m 3 r 8
Dist from O
B1 B1
(4 + k)m
km 1 − r 2
0
Moments about O: 3 1 r × 4m = r × km 8 2
M1
k =3
A1 (4)
(b)
30o O
G
λ mg
7mg
tan 30 = OG =
B1
OG r
λ
(7 + λ )
M1
× 2r
1 λ 1 = × 2r × √ 3 (7 + λ ) r
7 + λ = 2 √ 3λ 7 λ= 2 √ 3 −1
(
)
A1
A1
(o.e.) or 2.84
(4) [8]
GCE Mechanics M3 (6679) January 2011
2