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Heat problem

  • Thread starter epsbanga12
  • Start date
HI!

This problem has been killing me...

The Q is the following: A canon fires a canon ball which weighs 50 grams vertically at an initial speed of 600 m/s. 3 Km on top of the point where it was fired, the speed is only 50 m/s. calculate the heat during the canon ball rise.

I dont know how to use the kinetic formula in function with the energy formula, any help would be appreciated!
 
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The canon ball has a certain amount of kinetic energy from the start and a certain kinetic energy when the speed is 50 m/s (which is less). Some of the kinetic energy has been transformed to potential energy. The rest of the energy has been "lost" as heat etc.

Start: [tex]W_k[/tex]
Finish [tex]W_k + W_p + W_h[/tex]

Lets call the heat energy [tex]W_h[/tex] in this case although it isn't exactly correct index.
 
Thanks for clearing things up, Mattara.

So what would we eventually have to do to find Q, the heat produced?
 

Hootenanny

Staff Emeritus
Science Advisor
Gold Member
9,598
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Using Mattara's notation Q = Wh.

~H
 
so it would be Wh + Wp = -Wh ?
 

Hootenanny

Staff Emeritus
Science Advisor
Gold Member
9,598
6
Not quite, intially you have some kinetic energy. At the 'end' you have some kinetic energy, some potential and the rest as heat, therefore;

Initial Kinetic = Final Kinetic + Potential Energy + Heat

[tex]\frac{1}{2}mv_{i}^{2} = \frac{1}{2}mv_{f}^{2} + mgh + Q[/tex]

Can you go from here?

~H
 
Last edited:
hehe thanks Hootenanny
Actually, i meant Wk + Wp= -Wh, the former Wh was a typo...

But everything is clear now, thanks a lot to both of you!
 

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