Thursday, June 2, 2011

Physics assignment! please help. ?

1) the hottest temperature on a planet was 864 degree Fahrenheit recorded on Venus by the Soviet venera probe and the US pioneer Probe. The coldest place in the solar system is Pluto where the temperature is estimated at -360 degree fahrenheit. CALCULATE each of the temperature in degree Celsius.



2) The temperature of background radiation left over from big bang during the creation at the universe is 3 K (kelvin). What is the temperature of the universe in Fahrenheit and Celsius?



3) bradley, working in his 23 degree celsius kitchen, is cooking himself a crepe in an iron skillet that has a circular bottom with diameter of 30 cm. how hot must the skillet be in order for Bradley to make a 710.3 square cm crepe that just fill the bottom of the pan?



4) phoebe's insulated foam cup is filled with 0.150 kg of the coffee (mostly water) that is too hot to drink, so she adds 0.010 kg of milk at 5.0 degree celsius. if the coffee has an initial temperature of 70 degree celsius and the specific heat capacity of milk is 3800 J/kg, how hot is the coffee after the milk is added?



5) While Laurie is boiling water to cook spaghetti, the phone rings, and all 1.5 kg of water boils away duing her conversation. if the water was initially at 150 degree celsius, how much heat must have been gained for all of it to turn into water vapor? (Hv water = 2.26 x 10 (to the 6th power) j/kg



6) By january, the 3.0 kg of water in the birdbath in Daniel's backyard has frozen to a temperature at -7 degree celsius. as thje season changes how much heat must be added to water to make it confortable 25 degree celsius for the birds?



THANK YOU SO MUCH! :)Physics assignment! please help. ?
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螖E = 0



(m_water)(c_water) 螖t - (m_milk)(c_milk) 螖t' = 0



(0.15)(4186) (70 - t) - (0.01)(3800) (t - 5) = 0



t = 66.29掳CPhysics assignment! please help. ?
1) Formula to convert from Fahrenheit into Celsius:-

C = (5/9)*(F-32)



864 deg F = (5/9)*(864-32) = (5/9)*832 = 462 deg C

-360 deg F = (5/9)*(-360-32) = (5/9)*(-392) = -218 deg C

Ans: 462 deg C, -218 deg C



2) 3 K = 3 - 273 deg C = -270 deg C

Formula to convert from C into F:-

F = 9C/5 + 32

-270 deg C = 9*(-270)/5 + 32 = -454 deg F

Ans: -454 deg F, -270 deg C



3) Thermal expansivity of iron alpha = 12 * 10^-6 /deg C

Radius r = 30 cm/2 = 15 cm

Original area Ao = pi * (15 cm)^2 = 706.5 cm^2

Final area A = 710.3 cm^2

Change in area deltaA = 710.3 - 706.5 = 3.8 cm^2

Let change in temperature = deltaT

deltaA = 2 * alpha * Ao * deltaT

3.8 = 2 * 12 * 10^-6 * 706.5 * deltaT

3.8 = 0.016956 * deltaT

deltaT = 3.8/0.016956 = 224 deg C

Final temperature = initial temperature + deltaT = 23 + 224 = 247 deg C

Ans: 247 deg C



4) Coffee is mostly water.

Specific heat capacity of coffee cc = specific heat capacity of water = 4186 J/kg/deg C

Specific heat capacity of milk cm = 3800 J/kg

Initial temperature of coffee tic = 70 deg C

Initial temperature of milk tim = 5.0 deg C

Mass of coffee Mc = 0.150 kg

Mass of milk Mm = 0.010 kg

Let final temperature of the mixture = tf

Mc * cc * (tf - tic) + Mm * cm * (tf - tim) = 0

0.150 * 4186 * (tf - 70) + 0.010 * 3800 * (tf - 5.0)

627.9 * tf - 43953 + 38 * tf - 190 = 0

665.9 * tf - 44143 = 0

tf = 44143/665.9

tf = 66.3 deg C

Ans: 66.3 deg C



5) Mass m = 1.5 kg

Heat gained = m * Hv

= 1.5 * 2.26 * 10^6 J

= 3.39 * 10^6 J

Ans: 3.39 * 10^6 J



6) Initial temperature ti = -7 deg C

Final temperature tf = 25 deg C

Mass m = 3.0 kg

Specific heat capacity of water c = 4186 J/kg/deg C

Heat = m*c*(tf-ti)

= 3.0 * 4186 * [25 - (-7)]

= 3.0 * 4186 * 32

= 401856 J

= 4.02 * 10^5 J (rounded off)

Ans: 4.02 * 10^5 J



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