When traveling past an observer with a relative speed v, a rocket is measured to be 9.10 m long. when the rocket moves with a relative speed 2v, its length is measured to be 4.90 m?

Acapacitor is storing energy of 3 joules with a voltage of 50 volts across its terminals. a second identical capacitor of the same value is storing energy of 1 joule. what is the voltage across the terminals of the second capacitor?