To solve the problem it is necessary to apply conservation of the moment and conservation of energy.
By conservation of the moment we know that

Where
M=Heavier mass
V = Velocity of heavier mass
m = lighter mass
v = velocity of lighter mass
That equation in function of the velocity of heavier mass is

Also we have that 
On the other hand we have from law of conservation of energy that

Where,
W_f = Work made by friction
KE = Kinetic Force
Applying this equation in heavier object.






Here we can apply the law of conservation of energy for light mass, then

Replacing the value of 

Deleting constants,


Answer:
20n
Explanation:
60n - 40n = efficiency of pulley system
20n = efficiency of pulley system
Energy/power is not gained or lost going through a (ideal) transformer.
So the transformer in this problem really doesn't matter. If the lamp is using energy at the rate of 60 watts, then the whole contraption is getting 60 watts of power from the wall outlet.
Power = (voltage) x (current)
60 watts = (120 v) x (current)
Current = (60 watts) / (120 v)
<em>Current = 0.5 Ampere</em>
The correct ans is 1.
A changing electric field produces a changing magnetic field which in turn produces a changing electric field. This means that the source has created a changing electric and magnetic fields, perpendicular to each other, that travel away from the source. Electric field, magnetic field and the EM wave are perpendicular to each other. This gives electromagnetic waves their transverse nature.