Q26 of 27 Page 82

A thin rod having length L0 at 0° C and coefficient of linear expansion α has its two ends maintained at temperatures θ1 and θ2, respectively. Find its new length.

The length of the rod is L0. And the coefficient of linear expansion is α. Therefore, temperature (

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23

We would like to make a vessel whose volume does not change with temperature (take a hint from the problem above). We can use brass and iron (βvbrass = 6 × 10-5/K and βviron = 3.55 ×10-5 / K) to create a volume of 100 cc. How do you think you can achieve this?

24

Calculate the stress developed inside a tooth cavity filled with copper when hot tea at temperature of 57o C is drunk. You can take body (tooth) temperature to be 37o C and α = 1.7× 10-5 /o C, bulk modulus for copper = 140 × 10 9 N/m2.

25

A rail track made of steel having length 10 m is clamped on a railway line at its two ends (Fig 11.3). On a summer day due to rise in temperature by 20° C, it is deformed as shown in figure. Find x (displacement of the center) if αsteel = 1.2× 10-5 /°C.

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27

According to Stefans law of radiation, a black body radiates energy σT 4 from its unit surface area every second where T is the surface temperature of the black body and σ = 5.67 × 10-8 W/ m2K4 is known as Stefans constant. A nuclear weapon may be thought of as a ball of radius 0.5 m. When detonated, it reaches temperature of 106K and can be treated as a black body.

(a) Estimate the power it radiates.


(b) If surrounding has water at 30 C°, how much water can 10% of the energy produced evaporate in 1 s?


[Sw = 4186.0 J/ kgK and Lv = 22.6 X 105 J / kg]


(c) If all this energy U is in the form of radiation, corresponding momentum is p = U/c. How much momentum per unit time does it impart on unit area at a distance of 1 km?