2008 - WAEC Physics Past Questions and Answers - page 2
11
The mass attached to a string is moving in a circular path. If the speed is doubled, the tension in the string will be
A
doubled
B
halved
C
four times as great
D
one-fourth as much
correct option: c
Users' Answers & Comments12
An object of mass 2kg moving with a velocity 3ms-11 collides head-on with another object of mass 1kg moving in the opposite direction with a velocity of 4ms-1. If the objects stick together after collision, calculate their common speed.
A
0.60ms-1
B
0.67ms-1
C
2.00ms-1
D
3.33-1
correct option: b
\(M_1V_1 - (M_2V_2) = V(M_1 + M_2)\)
2 x 3 - 1 x 4 = V(2 + 1)
V = \(\frac{2}{3}\)
= 0.67ms-1
Users' Answers & Comments2 x 3 - 1 x 4 = V(2 + 1)
V = \(\frac{2}{3}\)
= 0.67ms-1
13
A ball is dropped and it hits the floor at a point A. It rebounds upward to a point B. While moving from A to B its
A
kinetic energy is increasing
B
potential energy is increasing
C
potential energy is decreasing
D
kinetic energy remains constant
correct option: a
The Kinetic Energy of a body is enrgy possessed by a body as a result of its motion. Hence, while in motion the kinetic energy of a body is increased.
14
Which of the following devices convert heat energy to electrical energy?
A
transformer
B
dynamo
C
thermocouple
D
thermostat
correct option: c
Users' Answers & Comments15
An object of mass 0.25kg moves at a height h above the ground with a speed of 4ms-1, if its mechanical energy at this height is 12 J, determine the value of h. [g = 10ms-1]
A
0.8m
B
4.0m
C
4.8m
D
5.6m
16
Which of the following equations for the efficiency of a machine is correct?
A
Efficiency = \(\frac{\text{Velocity Ratio}}{\text{Mechanical Advantage}}\) x 100%
B
Efficiency = \(\frac{input}{output}\) x 100%
C
Efficiency = \(\frac{\text{load distance}}{\text{effort distance}}\) x 100%
D
Efficiency = \(\frac{\text{Mechanical Advantage}}{\text{Velocity Ratio}}\) x 100%
correct option: d
Users' Answers & Comments17
The design of the thermostat of an electric iron is based on the
A
emmision of electrons from metals when heated
B
increase in size of metals when heated
C
increase in the density of metals when heated
D
change in the mass of metals when heated
correct option: b
Users' Answers & Comments18
A metal rod of length 50cm is heated from 40oC to 80oC. If the linear expansivity of the material is \(\alpha\), calculate the increase in length of the rod (in metres) in terms of \(\alpha\)
A
20\(\alpha\)
B
200\(\alpha\)
C
2000\(\alpha\)
D
20000\(\alpha\)
correct option: a
\(L_2 - L_1 = \alpha_1 (\theta_2 - \theta_1) = \alpha \times 0.5 \times 40 = 20 \alpha\)
Users' Answers & Comments19
The cubic expansivity of a certain gas at constant pressure is \(\frac{1}{273} k^{-1}\). If a given mass of the gas is held at constant pressure and its volume at 0oC is 273m3, determine the volume of the gas at 273oC.
A
273m3
B
546m3
C
8193
D
10923
correct option: b
\(V_2 = V_1(B\theta + 1) = 273 (\frac{1}{373} \times 273 + 1)\)
= 546m3
Users' Answers & Comments= 546m3
20
Water of mass 1.5kg is heated from from 30oC to 80oC using an electric kettle which is rated 5A, 230V. Calculate the time taken to reach the final destination [specific heat capacity of water 4200Jkg-1K-1]
A
4.57 minutes
B
5.02 minutes
C
7.30 minutes
D
10.04 minutes
correct option: a
t = \(\frac{MC\theta}{2} = \frac{1.5 \times 4200 \times 50}{5 \times 230}\)
= 273.91s or 4.57 mins
Users' Answers & Comments= 273.91s or 4.57 mins