a block (mass m1) on a smooth horizontal surface, connected by a thin cord that passes over a pulley to as second block (m2), which hangs vertically.

Ignore friction and the masses of the pulley and cord.

If m1 = 13.0 kg and m2 = 6.0 kg determine the accleeration of each block

for this I got about 3.09 s^-2 m

If initally m1 is at rest 1.250 m from the edge of the table, how long does it take to reach the edge of the table if the system is allowed to move freely?

for this I got about .90 s

ok this part I need help and possibly the other ones that I just did...

If m2 = 1.0 kg how large must m1 be if the acceleration of the system is to be kept at 100^-1 g

I imediately threw up the flag here because acording to our book the text says when g is not given use the magnitude of 9.80 so I took 100^-1 of that magnitude and got exactly 99 kg

can someone please confirm these answers?

Thank you!

3 answers

The answers are correct. In the last part, your answer does not depend on your choice for g. If you leave it undetermined it will factor out of your equations.

I think you should practice a bit with more complicated problems. I think that you get bogged down a bit too much in elementary math and that prevents you from mastering the actual physics.

A good problem would e.g. be to take the cord to be elastic such that the tension in the cord is given by
c(L-L0), where L is the length of the cord.

Write down the differential equations for the position of the two masses in this case. What are the initial conditions if mass 1 is held in place and mass 2 hangs and then we suddenly release mass 1 at t = 0?
Actually, this problem would be a bit too complicated as the tension in the string would not be uniform.
I'm confused, there is no explanation here and I REALLY need help on it!