Rope, Pulley, Scale Problem

A mass on a rope attached to a larger mass via a pulley. The larger mass is on a scale. What does the scale read? And what does a spring scale read that is holding up the pulley?

[@heysoymarvin]

It's crazy. It also means that the mass in a system is conserved, right? Because the total mass of the system is 600g and then it splits into two scales: 400g and 200g.

[@chenyuankhai3706]

Want to ask if the heavy load side is pulled with a constant acceleration, what will happen to the scale reading would it increase or decrease? Sir can u make an example upon my question? 🙏

[@Seyibabs123]

How would you calculate what it says on the spring scale if the pulley was moving?

[@cstephenmurray]

If the masses were moving the digital scale below would read zero. Then, assuming the pulley was frictionless and massless (some are very close), the spring scale would always read twice the tension in the string. To calculate the tension in the string would be an easy two mass system problem: (Mg)heavy - (mg)light = (M+m)a, to find “a” of the system; then use this a with either mass to calculate T.

[@holeshot1721]

Put some books up and see if that 100 gram weight is actully reading 100gs its def not cause u had to mechanical advantages one being the pulley the other being the spring on the scale ! So that 100grams is now less mass

[@cstephenmurray]

I'm not sure I follow what you are saying. The 100g mass is, of course, 100g. I could put it on an electronic balance to prove that, I guess. The only manipulation I did with this lab, was zero the spring scale so that its mass (the scale) was not part of the measurements. I really would, though, like to redo this video. I want to show the problem with the scales covered and them reveal the answers. There are also lots of ways to expand this lab. It really helped my students understand tension, which is much more complicated than it seems at first glance.