Physics Times 07.2019

(Kiana) #1

5.Sol:


[OFFLINE QUESTIONS]
1.Sol:


2.Sol:


3.Sol:

4.Sol:

5.Sol: The heat released by steam when it converts
from 100 C to 0 .C
     Q 10 540 10 1 100
The mass of the ice that melts is
    Q 6400 m 80 m 80 g
Water in calorimeter    500 80 10 590g


[OFFLINE QUESTIONS]
1.Sol: According to principle of calorimetry,
Heat lost = Heat gain
100 0.1       T 75 100 0.1 45 170 1 45


(^10) T   (^75)  450 7650
(^) T  885 C
2.Sol: Assume that radius is decreased by R
 mL AT
where m is the decrease in mass of the drop.
A is decrease in surface area. T is the
coefficient of surface tension.
 
4       R R L^24 T R^2 R R^2 
 
      R RL T R^2 ^2 R^22 R R R^2 
   R RL T R R^22 R is very small
R^2 T
L
 

3.Sol:    U Q mc T
=100 10   ^3 4184 50 30  8.4kJ
4.Sol: Required work = Energy released


Here, Qmc dT

4 3
3
20

0.1 32 0.002
400

   T dT kJ
 
 


Therefore, required work = 0.002 kJ.
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