if you're good in physics...?

Question

this is my worst subject. and if you could please give good explaination on how to solve the problem? --thanks

A 5.00 x 10^2 kg object is attached by a rope through a pulley to a paddle-wheel shaft that is placed in a well-insulated tank holding 25.0 kg of water. the object is allowed to fall, causing the paddle wheel to rotate, churning the water. if the object falls a vertical distance of 1.00 x 10^2 m at constant speed, what is the temperature change of the water? (cp= 4186 j/kg C and g= 9.81 m/s^2)

Answer 1

The energy transfered to the tank comes from the mass of 5x10² kg falling a distance of 1x10²m. The potential energy of the mass was
Ep = mgh = 500*9.81*100 = 490,500 J
Since the tank holds 25 kg of water, it will take
25*4186 = 104,650 J to raise it's temperature by 1 °C. Since we have put 490,500 J into the tank, the temperature rise will be
490,500/104,650 = 4.687 °C.

See how easy that is? ☺

Doug

Answer 2

hey don't worry.....dis is a pretty simple problem...
The potential energy of the mass was
E = mgh = 500*9.81*100 = 490,500 J
now this potential energy is converted to kinetic energy when the object of 5.00 x 10^2 kg is allowed to fall with a constant speed.......nd wen the object comes in contact with water......this kinetic energy gets converted to heat energy through frictional forcend this heat energy is used to raise the temp. of water
Since the tank holds 25 kg of water and the specific heat capacity of water is 4186 j/kg°C, it will take
25*4186 = 104,650 J to raise the temperature by 1 °C. now dividing this by total energy transferred to tank.we have

490,500/104,650 = 4.687 °C
i hope this might help clear ur doubt....gud luck wid physics

Answer 3

Potential energy lost by the object:

P = mgh = 500x9.81x100 N-m

Convert this energy into "joules" by looking up the conversion factor. Divide by 25.0kg and then by 4186. You should get your the temperature rise in "C".