A simple string light produces 10 J of light energy each second. What is the efficiency of the light bulb if it uses up 200 J each second?

With i really need the correct answer!

Astone is dropped with no initial velocity from the top of a cliff and hits the ground a time of 3.9 s later. what is the height of the cliff, in units of meters? you may assume that air resistance is negligible. give the answer as a positive number question 15 a figure skater is rotating at a rate of 200 revolutions per minute. what is the angular speed, in units of rad/s? 200 o 20.9 12000 o 3.33

Of is j/kg·k. if a 2.6 kg of isk to k,is ?