To solve this problem we will apply the concept related to the heat transferred to a body to reach a certain temperature. This concept is shaped by the energy ratio of a body which is the product of the mass, its specific heat and the change in temperature. For the specific case, it will be the sum of the heat transferred to the Water, the Aluminum and the loss due to latency due to vaporization in the water. That is to say,

Here,
= Mass of Aluminum
= Specific Heat of Aluminum
= Specific Heat of Water
Mass of water
Latent of Vaporization
Replacing,

Converting,


Therefore is required 440.409kCal
Answer:

Explanation:
We know that the frequency of the nth harmonic is given by
, where
is the fundamental harmonic. Since we have the values of two consecutive frequencies, we can do:

Which for our values means (we do not need the value of <em>n</em>, that is, which harmonics are the frequencies given):

Now we turn to the formula for the vibration frequency of a string (for the fundamental harmonic):

So the tension is:

Which for our values is:

Efficiency = (useful output) / (input)
Efficiency = (35 J) / (125 J) = 0.28 = 28%