A person heats up a can of soup on a stove. If he does 250 joules of work on the soup by stirring it as the burner adds 1675 joules of heat, what is the change in its internal energy?
I took 1675j - 250 j = 1425j
No. You add them.
Both stirring and heat addition increase the internal energy.
To find the change in internal energy of the soup, you need to consider the energy being added to it and the energy being removed from it.
In this case, 1675 joules of heat are being added to the soup by the burner, and 250 joules of work are being done on the soup by stirring.
The first step is to calculate the total energy being added to the soup. You correctly added the heat and work together: 1675 joules + 250 joules = 1925 joules.
So, the total energy being added to the soup is 1925 joules.
To find the change in internal energy, you need to subtract the energy being removed from the energy being added. In this case, no energy is being removed, so the change in internal energy is equal to the total energy being added.
Therefore, the change in internal energy of the soup is 1925 joules.