Friday
April 29, 2016

# 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 10°C, has a coefficient of linear expansion of 11 ´ 10-6/C°. Give its change in length as the temperature changes from 10°C to 45°C.

5.8 cm

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

30 × 10-6/°C

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

105°C

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 0°C. 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/kg×°C, 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/s×m×°C.)

2 500 J/s

6 A 10-kg piece of aluminum (which has a specific heat of 900 J/kg×°C) 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?

33%

8 A 2.00-kg block of ice is at STP (0°C, 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°