EQUILIBRIUM OF FORCES
1 (a)
(i)
Define a couple.
(ii)
(b)
State two conditions for a body to be in equilibrium. [3]
Fig .10.1 shows a horizontal uniform beam of length 8 m and weight
200 N. The beam is pivoted at a wall with one of its ends connected to
a metal cable of an angle of depression of 530. A mass weighting 600
N is place 2 m from the wall. A reaction force, R, acts at the pivot, P,
at an angle, θ, to the horizontal.
530
cable
R
Wall
θ
Books
530
O
8m
P
Fig. 10.1
600 N
Calculate the
(i)
Tension in the cable,
(ii)
Reaction force, R,
(iii)
Angle θ.
[6]
(c)
Give one example of everyday application of forces in equilibrium. [1]
(d)
The system shown in Fig.11.2 is in equilibrium.
c
b
600
Fig.11.2
200
a
M
If M = 2.0 kg, find the magnitude of the tension in
2
(i)
String ab,
(ii)
String bc
[4]
(a)
Explain the term centre of gravity of an object.
[2]
(b)
A uniform beam, AB, 2 m long and of weight 80 N, is in equilibrium. It has 70
N. Load places 0.20 m from end B and an unknown load of weight, W, placed
0.3 m from end A. P is the pivot 0.50m from end A.
3
(i)
State two conditions required for the beam to be in equilibrium.[2]
(ii)
Determine the weight of the load, W.
[4]
(a)
Define torque of a couple and state its base units.
[3]
(b)
Fig. 3.1 shows a uniform wooden board of mass 3.0 kg and length 40.0 cm
used as a book shelf. The board is supported by a light string from end A to
the wall at an angle of 360. Two books of mass 1.5 kg each are placed such
that their centre of mass is 25.0 cm from the hinge.
Calculate
(i)
The tension in the string
(ii)
The force exerted by the hinge
[7]
B
T
Wall
Books
360
A
O
40.0 cm
Hinge
4
(a)
(i)
Fig. 3.1
State two conditions for coplanar forces acting on a body to be in
equilibrium.
(ii)
Fig 13.1 shows a 65.0 kg man standing close to the edge of a balcony.
The balcony has a weight of 3 450 N acting at a point 2.10 m from the
wall. A supporting cable, S, keeps the system horizontal.
Cable S
500
wall
0.55 m
P
Fig.13.1
0.9 m
2.10 m
Calculate the
1. Tension in S,
2. ,.cReaction force at P.
[6]