EK physics 1001 (245)

[Spiker]

Two mass A and B. A=m B=2m

What is the tension when the mass become infinitely large?

I put infinite because the tension is 1.33mg.

However the book says 1000N which I dont see how they can get that? lol...

Can someone confirm?

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[Fortify]

Bump for answer?

The question shows two masses connected by a string on either side of a massless, frictionless pulley of mass m and 2m. They ask what the tension in the rope would be if the mass 2m was increased to infinity

My thinking

Let's call mass m A, and what was mass 2m B

FnetA = T - mg

mAaA = T-mAg, since the other mass is infinite, a = g upwards for this mass
mAg = T - mAg
T = 2mAg

For the second mass, FnetB = T - inf(g)
2(inf)(g) = T, T = inf(g)

How can you reconcile this? The book says 1000N is the tension which is clearly wrong..

 

[MT Headed]

It's a misprint. The question talks about "the mass" in "the problem above". Unfortunately the problem above contains two masses. Question 245 was referring back to problem 242.

See if you can solve it now. If you solved question 243 it shouldn't be too hard.