A jet fighter with a mass of 20,000 kg coasts through the sky at an altitude of 10 km and a velocity of 250 m/s. The jet then dives to an altitude of 2 km. Find the new velocity of the jet.

Question

A jet fighter with a mass of 20,000 kg coasts through the sky at an altitude of 10 km and a velocity of 250 m/s. The jet then dives to an altitude of 2 km. Find the new velocity of the jet. All forces acting on the system are conservative.

Answer 1

Well if we assume mechanical energy is conserved

At 10 km, PE = mgh = 20000 x 9,81 x 10000 and KE is 0.5mv² = 0.5 x 20000 x 250²

So PE + KE = PE and KE at 2 km, which is 20000 x 9.81 x 2000 + 0.5 x 20000 x v²

The mass cancels

so 9.81 x 10000 + 0.5 x 250² = 9.81 x 2000 + 0.5 v²

^{Solve for v}