Explanation:
the table and the wooden block
Answer:
If by 1.5 MJ you mean 1.5E6 Joules then
W = P t = power X time
W / t = P power
P = 1.5E6 J / 600 sec = 2500 J / s
P = I V
a) I = 2500 J/s / (240 J/c) = 10.4 C / sec = 10.4 amps
b) Q = I t = 10.4 C / sec * 300 sec = 3120 Coulombs
c) E = P * t = 2500 J / sec * 100 hr * 3600 sec / hr = 9.0E8 Joules
A vibrating stretched string has nodes or fixed points at each end. The string will vibrate in its fundamental frequency with just one anti node in the middle - this gives half a wave.

Rearranging for the wavelength



Therefore the longest wavelength standing wave that it can support is 14m
The battery doesn't 'use' power. The battery <em>produces</em> the power that all the other electrical devices use.
If the starter motor is using 2,520 watts, then the battery is producing energy at the rate of 2,520 watts. That means <em>2,520 Joules</em> of energy every second.
Thanks for giving us the formula.
E = P x t
Energy = Power x Time
Energy = (2,520 watts) x (1 second)
Energy = 2,520 Joules