(a)
Principle of moments
For
equilibrium / balance
sum
of moments clockwise = sum of moments anti-clockwise
or
sum of moments (about a point) is zero
[Sum
or equivalent eg total/net/resultant [NOT all] must be seen at least
once]
2
(b)(i)
Weight of retort stand
Use
of principle of moments
i.e.180
× (10-3 m)
× W = 228 × (10-3 m)
× 9 (N)
[Allow
1 wrong distance]
11.4
(N)
[At
least 3 sig fig required. No u.e.] [In this question allow reverse
calculation
to gain full marks] [Bald answer scores 0]
2
(ii)
Reading on newtonmeter and normal contact
Fully
correct moment equation
F × 448 × (10-3 m) = 11.4 (N) ×40 × (10-3
m)
[allow
11 N × 40 × (10-3)
m or ecf from bi]
=
1.0 N
Normal
contact force (11.4 N/11 N − 1 N) = 10.4 N or 10 N (upwards)[ecf
