The mechanical advantage of a machine is the ratio between the output force and the input force:

In our problem, the input force is 100 N, while the output force is the weight of the object the student lifts, 500 N. So, the mechanical advantage is
50 because read step by step explanation
Answer:
See the answers below.
Explanation:
The total power of the circuit is equal to the sum of the powers of each lamp.
![P=60+100\\P=160 [W]](https://tex.z-dn.net/?f=P%3D60%2B100%5C%5CP%3D160%20%5BW%5D)
Now we have a voltage source equal to 240 [V], so by means of the following equation we can find the current circulating in the circuit.

where:
P = power [W]
V = voltage [V]
I = current [amp]
![I = P/V\\I=160/240\\I=0.67 [amp]](https://tex.z-dn.net/?f=I%20%3D%20P%2FV%5C%5CI%3D160%2F240%5C%5CI%3D0.67%20%5Bamp%5D)
So this is the answer for c) I = 0.67 [amp]
We know that the voltage of each lamp is 240 [V]. Therefore using ohm's law which is equal to the product of resistance by current we can find the voltage of each lamp.
a)

where:
V = voltage [V]
I = current [amp]
R = resistance [ohms]
Therefore we replace this equation in the first to have the current as a function of the resistance and not the voltage.

![60 = (0.67)^{2}*R\\R_{60}=133.66[ohm] \\and\\100=(0.67)^{2} *R\\R_{100}=100/(0.66^{2} )\\R_{100}=225 [ohm]](https://tex.z-dn.net/?f=60%20%3D%20%280.67%29%5E%7B2%7D%2AR%5C%5CR_%7B60%7D%3D133.66%5Bohm%5D%20%5C%5Cand%5C%5C100%3D%280.67%29%5E%7B2%7D%20%2AR%5C%5CR_%7B100%7D%3D100%2F%280.66%5E%7B2%7D%20%29%5C%5CR_%7B100%7D%3D225%20%5Bohm%5D)
b)
The effective resistance of a series circuit is equal to the sum of the resistors connected in series.
![R = 133.66 + 225\\R = 358.67 [ohms]](https://tex.z-dn.net/?f=R%20%3D%20133.66%20%2B%20225%5C%5CR%20%3D%20358.67%20%5Bohms%5D)