Physics Test 91

Result

Physics Test 91

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Question 1
4 / -1

1 kg ice at –10°C is mixed with 4.4 kg water at 30°C. Final temperature of mixture :

A
2.3°C

B
4.4°C

C
5.3°C

D
8.7°C

Solution

Heat lost = Heat gained
4.4 × 1 × [30 – T]
= 1 × 0.5 × 10 + 1 × 80 + 1 × [T – 0]
T = 8.7°C
Question 2
4 / -1

10 g ice at 0°C is kept in a container of water equivalent 10 g. How much heat must be supplied to evaporate the water thus formed :

A
6200 cal

B
7200 cal

C
13600 cal

D
8200 cal

Solution

Q = 10 × 80 + 20 × 1 × 100 + 10 × 540
= 8200 cal
Question 3
4 / -1

Ratio of co-efficient of thermal conductivity of two materials is 5 : 3. If thermal resistance of rods of same area of these materials is same, find ratio of lengths :

A
3 : 5

B
5 : 3

C
25 : 9

D
9 : 25

Solution
Question 4
4 / -1

Three identical rods are arranged as shown. Find temperature of junction :

A
45°C

B
60°C

C
30°C

D
20°C

Solution
Question 5
4 / -1

A spherical body of area A and e = 0.6 is kept inside a black body. Find power radiated at temperature T :

A
0.6 σAT⁴

B
0.4 σAT⁴

C
0.8 σAT⁴

D
1 × σAT⁴

Solution

P = σeAT⁴
Question 6
4 / -1

Liquid takes 30 s to cool from 95°C to 90°C and 70s cooling from 55°C to 50°C. Temperature of room is :

A
16.5°C

B
22.5°C

C
28.5°C

D
32.5°C

Solution

5/30 = k[92.5 – T_S]
5/70 = k[52.5 – T_S]
⇒ T_S = 22.5°C
Question 7
4 / -1

Which of the substance A, B or C of same mass has the highest specific heat, if heat is given to A, B and C at same rate ? The temperature v/s time graph is shown :-

A
A

B
B

C
C

D
All have equal specific heat

Solution

Substance having more specific heat taken longer time to get heated to a higher temperature and longer time to get cooled. If we draw a line parallel to the time axis then it cut the graph at three different points. Corresponding points on the time axis shows that

t_C > t_B > t_A ⇒ C_C > C_B > C_A
Question 8
4 / -1

A gas is filled in the cylinder shown in the figure. The two piston are joined by a string. If the gas is heated, the piston will :-

A
Move towards left

B
Move towards right

C
Remain stationary

D
None of these

Solution

On heating pressure ()
As force on right side is more as compared to left so piston will shift in right direction.
Question 9
4 / -1

A cyclic process ABCA is shown in P-T diagram. What would be its P-V graph :-

A

B

C

D
Question 10
4 / -1

An ideal gas at a pressure of 1 atm and temperature of 27°C is compressed adiabatically until its pressure becomes 8 times the initial pressure, the final temperature is (γ = 3/2) :-

A
627°C

B
527°C

C
427°C

D
327°C

Solution