3.
(a) Principle of moments
In
equilibrium
sum
of clockwise moment (about any point) is equal to sum of
anticlockwise
moment (about that point)
2
(b)(i)
Weight
Use
of “width x thickness x length”
Use
of “density = mass”
volume
Correct
value 3
V = 1.2 × 0.6 × 200
(cm3)
= 144 (cm3)
Using
ρ = m/v
m = 8 (g cm-3) × 144 (cm-3) = 1152 g
Weight
= mg = 1152 × 10-3
(kg) × 9.81
( m s-2)
= 11.3 (N) / 12
(N)
(ii)
Force F
Correct
substitution into correct formula
Correct
value with correct unit
F × 60
(cm) = 11.3 (N) ×
40 (cm) / 12 (N) × 40 (cm) / 11(N) × 40
(cm)
=
7.5 N / 8 N / 7.3 N
2
(iii)
Force R
18.3
N / 18.8 N / 20 N
1
(iv)
Sketch graph
Any
line upwards
Correct
shape for F [concave shaped curve]
2
