2002 - WAEC Physics Past Questions and Answers - page 2
11
An object A is held in equilibrium as illustrated in the diagram above. Using the data on the diagram determine the magnitude, W of the weight of
A
23N
B
17N
C
7N
D
5N
12
A spiral spring of natural length 30.0cm and force constant of 20Nm-1 is compressed to 20.0cm. Calculate the energy stored in the spring
A
0.1J
B
1.0J
C
10.0J
D
100.0J
correct option: a
Energy = \(\frac{1}{2} ke^2 = \frac{1}{2} \times 20 \times 0.1^2\)
= 0.1J
Users' Answers & Comments= 0.1J
13
In the diagram above, AB represents a uniform rod of length 1.50m which is in equilibrium on a pivot at P, If AP = 40cm, calculate the mass of the rod. [g = 10ms-2]
A
0.280kg
B
0.400kg
C
0.613kg
D
0.800kg
14
Which of the following statements correctly defines quantitatively the work done by a force? the product of the force and the distance moved
A
parallel to the line of action of the force from a reference point
B
perpendicular to the line of action of the force from a reference point
C
on a line through the reference point
D
by the object
correct option: a
The quantity of work done (or energy converted) by a force, when the force moves, depends on two obvious factors:
- the distance moved (in the direction along which the force acts) and
- the magnitude (strength) of the force
15
a load of mass120kg is raised vertically through a height of 2m in 30s by a machine whose efficiency is 100%. Calculate the power generated by the machine. [g = 10ms-2]
A
60W
B
80W
C
100W
D
120W
correct option: b
p = \(\frac{mgh}{t} = \frac{120 \times 10 \times 2}{30} = 80W\)
Users' Answers & Comments16
A block and tackle system has 6 pulleys. If the efficiency of the machine is 60%, determine its mechanical advantages
A
12.0
B
10.0
C
3.6
D
1.8
correct option: c
M.A = \(\frac{Z \times V.R}{100} = \frac{60 \times 5}{100} = 3.6\)
Users' Answers & Comments17
Which of the following actions will improve the efficiency of the pulley system?
A
reducing the mass of the pulley
B
increasing the friction force between the string and the pulley
C
increasing the mass per unit length of the string of the pulley
D
increasing the mass of the pulley
correct option: a
Users' Answers & Comments18
The ice and steam points of a certain thermometer are -20o and 100o respectively. Calculate the Celsius temperature temperature corresponding to 70o on the thermometer
A
84.0o
B
75.0o
C
64.0o
D
58.0o
correct option: b
\(\frac{70 - 20}{100 - 20} = \frac{\theta - 0}{100 - 0}\)
\(\theta = \frac{90 \times 100}{120} = 75^oC\)
Users' Answers & Comments\(\theta = \frac{90 \times 100}{120} = 75^oC\)
19
The silver coating on the inside of a vacuum flask reduces heat loss by
A
conduction
B
radiation
C
condensation
D
convention
correct option: b
Users' Answers & Comments20
Water of mass 120g at 50oC is added to 20og of water at 10oC and the mixture is well stirred. Calculate the temperature of the mixture. [Neglect heat losses to the surrounding]
A
60oC
B
40oC
C
25oC
D
10oC
correct option: c
120 x 4.2(50 - \(\theta\)) = 200 x 4.2(\(\theta\) - 10)
\(\theta = \frac{33600}{1344} = 25^oC\)
Users' Answers & Comments\(\theta = \frac{33600}{1344} = 25^oC\)