Respuesta :
36 Joules
Explanation
the work done is the amount of energy transmited ( the change of energy)
Step 1
find the potential energy at the moment before the birds falls
the potential energy is given by :
[tex]\begin{gathered} E_p=mgh \\ \text{where} \\ m\text{ is the mass } \\ g\text{ is the acceleration due to gravity} \\ \text{and h is the height, so} \end{gathered}[/tex]let
m= 400g=0.4 kg
replace
[tex]\begin{gathered} E_p=mgh \\ E_p=0.4\text{ Kg}\cdot9.8m\frac{m}{s^2}\cdot10m \\ E_p=39.2\text{ Joules} \end{gathered}[/tex]Step 2
now, the energy at the bottom
when the bird is the bottom it has kinetic energy, it is given by the expression
[tex]\begin{gathered} E_k=\frac{1}{2}mv^2 \\ \text{where m is the mass} \\ \text{and v is the velocity of the object} \end{gathered}[/tex]then,
let
m=0.4 kg
v=4 m/s
replace.
[tex]\begin{gathered} E_k=\frac{1}{2}mv^2 \\ E_k=\frac{1}{2}(0.4kg)(4\frac{m}{s})^2 \\ E_k=\frac{1}{2}(0.4kg)(16\frac{m^2}{s^2}) \\ E_k=3.2\text{ Joules} \end{gathered}[/tex]Step 3
finally, the work done by the air resitance, is the difference of the energy ,so
[tex]\begin{gathered} \text{Work done(w)=E}_f-E_i \\ \text{replace} \\ W=3.2\text{ J-}39.2 \\ W=-36\text{ Joules} \end{gathered}[/tex]the negative sign indicates that the work done by the air was against the movement of the bird
therefore, the answer is
36 Joules
I hope this helps you
