Very Basic Physics that I'm struggling on

[aguycalledwil]

Very Basic Physics...that I'm struggling on...

Homework Statement

In an experiment to find the temperature of a Bunsen flame, a 0.2kg brass mass is heated in the flame. The hot mass is then placed in a beaker containing 0.2 kg of water. The temperature of the water rises from 20C to 80C.
a)what is the rise in temperature of the water?
b)what is the heat energy gained by the water?
c)assuming the temperature of the mass to be T, what is the fall in temperature of the mass?
d)what is the heat lost by the mass?
e)assuming that the heat lost by the mass is the same as the heat gained by the water, find the temperature, T.

Homework Equations

H=m*c*rise in temperature

The Attempt at a Solution

I think I have the first four. I did...
a) 80C-20C = 60C
b) H=0.2*4200*60 = 50400J
c) H/mc=change in temp. therefore, -50400/0.2*370=change in temp. therefore, the change in temp. is -681C
d) I just assumed that the the heat lost by the mass is the same as the heat gained by the water, which is 50400J.
e) This one has me completely stuck...

 

[willem2]

In an experiment to find the temperature of a Bunsen flame, a 0.2kg brass mass is heated in the flame. The hot mass is then placed in a beaker containing 0.2 kg of water. The temperature of the water rises from 20C to 80C.
a)what is the rise in temperature of the water?
b)what is the heat energy gained by the water?
c)assuming the temperature of the mass to be T, what is the fall in temperature of the mass?
d)what is the heat lost by the mass?
e)assuming that the heat lost by the mass is the same as the heat gained by the water, find the temperature, T.

The Attempt at a Solution

I think I have the first four. I did...
a) 80C-20C = 60C
b) H=0.2*4200*60 = 50400J
c) H/mc=change in temp. therefore, -50400/0.2*370=change in temp. therefore, the change in temp. is -681C
d) I just assumed that the the heat lost by the mass is the same as the heat gained by the water, which is 50400J.
e) This one has me completely stuck...

you already computed the temperature loss of the brass. The brass ends up at the same temperature of the water after losing 681 degrees

 

[tomcue]

I would first like to commend you on your effort in solving the problem and finding the correct answers for parts a-d. However, I would like to point out a few things that may help you understand the concept better.

For part c, the change in temperature of the mass should be a negative value since it is losing heat and therefore, its temperature will decrease. So, the correct answer would be -681C.

For part d, it is true that the heat lost by the mass is the same as the heat gained by the water. However, in order to find the heat lost by the mass, we need to use the formula H=m*c*change in temperature. In this case, the mass is losing heat, so its change in temperature would be negative. Therefore, the heat lost by the mass can be calculated as -0.2*370*(-681) = 50400J, which is the same as the heat gained by the water.

For part e, we can use the fact that the heat lost by the mass is equal to the heat gained by the water. So, we can set up the equation -0.2*370*(T-20) = 50400J, where T is the temperature of the mass. Solving for T, we get T = 20 + 50400/(0.2*370) = 20 + 681C = 701C. This would be the temperature of the mass after it has lost heat to the water.

Overall, it seems like you have a good understanding of the basic physics concepts involved in this problem. Keep up the good work and don't hesitate to ask for help if you are struggling with any other concepts.