# Work done on the jet by the catapult

1. Feb 23, 2008

### kittymaniac84

1. The problem statement, all variables and given/known data

A fighter jet is launched from an aircraft carrier with the aid of its own engines and a steam-powered catapult. The thrust of its engines is 3.14 x 10^5 N. In being launched from rest it moves through a distance of 85.1 m and has a kinetic energy of 5.63 x 10^7 J at lift-off. What is the work done on the jet by the catapult?

2. Relevant equations

w=sumF*displacement=0.5mv$$^{2}_{f}$$-0.5mv$$^{2}_{o}$$

3. The attempt at a solution

I am unsure how to start this. They dont give me the final velocity or the mass. so I dont think i can use that equation. Is this a tricky question? Is the answer 5.63 x 10^7 J or 5.63 x 10^7 J times 85.1m= 4.79 x 10^9
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Feb 23, 2008

### lavalamp

You can calculate the word done by the engines with:
W = Fd

Then subtract it from the final kinetic energy, the remainder will be the work done by the catapult.

3. Feb 23, 2008

### Littlepig

so, considering there's no atrit and no potencial energy variation and that fuel is massless , have 2 vital information:
W=sum(F*r)
total work=delta Energy(in case Potencial energy=constant, total work=delta kinectic Energy).

So, you have
Energy in the begin and Energy in the end

and than you know that total work=W1+W2 (where W1 is work of jets and W2 work of catapult)

I guess you have all...(i don't make the calculations as i prefer letters ratter than numbers...)

4. Feb 23, 2008

### kittymaniac84

ok that makes sense now. thank you