If a light bulb is said to be 20% efficient, what does it mean

If two metal balls each have a charge of -10^-6 c and the repulsive force between them is 1 n, how far apart are they? (coulomb's constant is k = 9.0x 10^9 n-m^2/c^2? 9.5 m 9.0 mm 9.5 cm 0.9 m .

Eddy whose mass is 55kg climbs up the 1.50 meter high stairs in 2s.calculate eddy’s power rating

Drag each item into the proper state of matter category.