# 1995 - WAEC Physics Past Questions and Answers - page 2

11

A mercury-in-glass thermometer reads - 20

^{o}at the ice point and 100^{o}at the steam point. Calculate the celcius temperature corresponding to 70^{o}on the thermometer.A

41.0

^{o}CB

50.0

^{o}CC

62.5

^{o}CD

70.0

^{o}C**correct option:**e

12

A brass rod is 2 m long at a certain temperature. Calculate the linear expansion of the rod for a temperature change of 100K. (Take the linear expansivity of brass as 1.8 x 10'5K").

A

0.3600 m

B

0.1800 m

C

0.0360 m

D

0.0036m

**correct option:**d

13

A body of specific heat capacity 450J kg

^{-1}K^{-1}falls to the ground from rest through a vertical height of 20m. Assuming conservation of energy, calculate the change in temperature of the body on striking the ground level. (g = 10ms^{-2})A

0

^{o}CB

2/9

^{o}CC

4/9

^{o}CD

9/4

^{o}C**correct option:**c

14

Hot water at a temperature of t is added to twice that amount of water at a temperature of 30°C. If the resulting temperature of the mixture is 50°C. Calculate t.

A

90

^{o}CB

80

^{o}CC

50

^{o}CD

40

^{o}C**correct option:**a

Final Temperature = \(\frac{m_1 T_1 + m_2 T_2}{m_1 + m_2}\)

where m\(_1\) and m\(_2\) are the weights of the water in the first and second containers.

T\(_1\) and T\(_2\) are the temperatures of the water in the first and second container.

Given Final temperature = 50°C;

Let m\(_1\) = b, then m\(_2\) = 2b.

T\(_1\) = t; T\(_2\) = 30°C

\(\therefore 50 = \frac{b(t) + 2b(30)}{b + 2b}\)

\(50 = \frac{bt + 2b(30)}{3b}\)

\(50(3b) = bt + 2b(30) \implies 150b = b(t + 60)\)

\(150 = t + 60 \implies t = 150 - 60 = 90°C\)

15

An air bubble of volume 2 cm* is formed 20 m under water. What will be its volume when it rises to just below the surface of the water if the atmospheric pressure is equivalent to a height of 10 m of water?

A

6cm

^{3}B

4cm

^{3}C

3cm

^{3}D

2cm

^{3}**correct option:**b

16

The pressure of a given mass of gas changes from 200 Nm

^{2}to 100 N m^{2}, while its temperature drops from 127^{o}C to - 73^{o}C. Calculate the radio of the final volume of the gas to its initial volume.A

2.4:1

B

2.0:1

C

1.2:1

D

1.0:1

**correct option:**d

17

The temperature of glass vessel containing 100cm3 of mercury is raised from 10

^{o}C to 100^{o}C. Calculate the apparent cubic expansion of the mercury. (Real cubic expansivity of mercury = 1.82 x 10^{-4}K^{-1}) (Cubic expansivity of glass = 2.4 x 10^{-5}K^{-1})A

0.52cm

^{3}B

1.42cm

^{3}C

1.87cm

^{3}D

5.22cm

^{3}**correct option:**b

18

An iron rod of mass 2kg and at a temperature of 280

^{o}C is dropped into some quantity of water initially at a temperature of 30^{o}C. lf the temperature of the mixture is 70^{o}C, calculate the mass of the water. (Neglect heat losses to the surroundings). Specific heat capacity of iron = 460 J kg^{}K^{}) (Specific heat capacity of water = 4200 Jkg^{}K^{})A

0.58kg

B

0.77kg

C

1.15kg

D

1.50kg

**correct option:**c

19

How much heat is required to convert 20 g of ice at 0

^{o}C to water at the same temperature? (Specific latent heat of ice = 336 J g^{-1})A

1.35 x 10

^{3}JB

5.38 x 10

^{3}JC

6.72 x 10

^{3}JD

7.06 x 10

^{3}J**correct option:**c

20

When two objects P and Q are supplied with the same quantity of heat, the temperature change in P is observed to be twice that in Q. lf the masses of P and Q are the same, calculate the ratio of the specific heat capacities of Q to P.

A

4 : 1

B

2 : 1

C

1 : 1

D

1 : 2

**correct option:**d