pulleys and Tension question

[greenseeking]

Which of the following systems are an advantage of pulley system I over pulley system II?
Please see attached picture

I. pulley system I provides a mechanical advantage
II. TEnsion in the cable is less in pulley System I
III. pulley system I ocupies less vertical space.

Answer is I Only.

Why isn't II true? Since Pulley system I has a mechanical advantage of 4, shouldn't the Tension of the rope be reduced by 4?
For I:
4T-mg=Fnet
T=Fnet+mg/4

For II:
T-mg=Fnet
T=Fnet+mg

---

Members don't see this ad.

 

[Testosterone]

Assuming F is the same in both systems, the tension always stays the same along the cable. A pulley only changes the direction of the tension across a cable, not the magnitude.