To solve this problem it is necessary to apply the concepts related to rate of thermal conduction

The letter Q represents the amount of heat transferred in a time t, k is the thermal conductivity constant for the material, A is the cross sectional area of the material transferring heat,
, T is the difference in temperature between one side of the material and the other, and d is the thickness of the material.
The change made between glass and air would be determined by:





There are two layers of Glass and one layer of Air so the total temperature would be given as,




Finally the rate of heat flow through this windows is given as,



Therefore the correct answer is D. 180W.
Answer:
2.67 m
Explanation:
k = Spring constant = 1.5 N/m
g = Acceleration due to gravity = 9.81 m/s²
l = Unstretched length
Frequency of SHM motion is given by

Frequency of pendulum is given by

Given in the question


The unstretched length of the spring is 2.67 m
Answer:
Option e) 320 s
Explanation:
Here, distance = 3.0 km = 3000 m
The velocity of boat when it is going upstream;
Upstream velocity = velocity of boat in still water - velocity of river flow
So, Upstream velocity 
So,Time to go upstream

The velocity of boat when it is going downstream;
Downstream velocity = velocity of boat in still water + velocity of river flow
So, Downstream velocity 
So,Time to go downstream

So, total time (t) = 
Option E is the correct answer.
From the law of Galileo Galilei :v²=v₀²+2ad we take the speed
v²=0+2*4.90*200=1960=>v=√1960=44.27 m/s