January 27, 2015

Homework Help: Physics

Posted by Jesse on Thursday, December 16, 2010 at 7:23pm.

I have ten problems left on my homework that I need help with. My instructor gives us the answer and we have to write down the steps. So if anyone could help me I would really appreciate it.

1 A steel wire, 150 m long at 10C, has a coefficient of linear expansion of 11 10-6/C. Give its change in length as the temperature changes from 10C to 45C.

5.8 cm

2 A pipe of length 10.0 m increases in length by 1.5 cm when its temperature is increased by 90F. What is its coefficient of linear expansion?

30 10-6/C

3 Carbon dioxide forms into a solid (dry ice) at approximately -157F. What temperature in degrees Celsius does this correspond to?


4 A 0.003 0-kg lead bullet is traveling at a speed of 240 m/s when it embeds in a block of ice at 0C. If all the heat generated goes into melting ice, what quantity of ice is melted? (Lf = 80 kcal/kg, the specific heat of lead = 0.03 kcal/kgװC, and 1 kcal = 4 186 J)

2.6 10-4 kg

5 A windowpane is half a centimeter thick and has an area of 1.0 m2. The temperature difference between the inside and outside surfaces of the pane is 15 C. What is the rate of heat flow through this window? (Thermal conductivity for glass is 0.84 J/smװC.)

2 500 J/s

6 A 10-kg piece of aluminum (which has a specific heat of 900 J/kgװC) is warmed so that its temperature increases by 5.0 C. How much heat was transferred into it?

4.5 104 J

7 A heat engine exhausts 3 000 J of heat while performing 1 500 J of useful work. What is the efficiency of the engine?


8 A 2.00-kg block of ice is at STP (0C, 1 atm) while it melts completely to water. What is its change in entropy? (For ice, Lf = 3.34 105 J/kg)

2 450 J/K

9 If a 1000-kg car was moving at 30 m/s, what would be its kinetic energy expressed in the unusual (for kinetic energy) units of calories? (1 cal = 4.186 J)

1.1 105

10 A puddle holds 150 g of water. If 0.50 g of water evaporates from the surface, what is the approximate temperature change of the remaining water? (Lv = 540 cal/g)

1.8 C

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