Q.If a comet suddenly hits the Moon and imparts energy which is more than the total energy of the Moon, what will happen?

Step 1. The Moon's current total energy in orbit is $E_{Moon}=K.E.+U<0$ -- negative, meaning it is gravitationally bound to the Earth.

Step 2. If a comet impact adds energy $\Delta E$ that is more than $|E_{Moon}|$ (the magnitude of the Moon's current, negative total energy), the Moon's new total energy $E_{Moon}+\Delta E$ becomes positive.

Step 3. A positive total energy means the Moon now has more kinetic energy than the (negative) potential energy could ever bind -- exactly the condition for an object to escape completely to infinity (the same energy condition used to define escape speed), rather than the negative-energy condition for a bound, closed orbit. …

Compare the imparted energy against the Moon's current (negative) total energy, and identify what a resu …

• Assuming any extra energy just changes the Moon's orbit shape/speed, without recognising that ENOUGH extra energy crosses the bound/u …