Energy conservation is important for houses. to what fraction is the heat transfer rate reduced by replacing a glass window 3 ft wide and 5 ft high with a smaller window 2 ft wide by 3 ft high? as a typical case, assume the outside temperature in the winter is 25°f and the inside temperature is 75°f. for this example assume u = 5.5 btu/(hr)(ft2)(°f)

Explanation:

Given

Initial Area of glass window is

Area of second window

And Heat transfer is given by

where k=thermal conductivity

dT=Temperature difference

dx=Thickness

Assuming k,\Delta T and thickness remains same

----1

----2

dividing 1 & 2

Thus

Thus heat is reduced by 60 %

the answer would be   dignified - apex

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.