Two blocks of masses m1=2kg and m2=5kg hang over a massless pulley as in the figure. A force F=100N acting on the axis of the pulley accelerates the system upward. Find : a) the acceleration of each block b) the tension in the string.

Question

yrelhan4 · Answer

attachment

yrelhan4 · Answer

answer: 2 kg block accelerates 15.2 m/s^2 upward
the 5 kg block accelerates .2 m/s^2 upward

yrelhan4 · Answer

30/7 ? g=10m/s2

3psilon · Answer

How would this problem be done with the force acting on the axis? that is new to me

yrelhan4 · Answer

@3psilon it just means the system is pulled by a force upwards, i guess.

3psilon · Answer

ok let me fool around with it and I'll see if I get that answer

yrelhan4 · Answer

right!

3psilon · Answer

So usually in an Atwell problem like this the acceleration is the same right? But I guess that force changes the acceleration of both?

yrelhan4 · Answer

yes.. acceleration of both the blocks without the force is 30/7 m/s2 .. if that could help..

vincent-lyon.fr · Answer

Actually, this problem is simpler than an Atwood machine.

Since the pulley is massless, it is very easy to find the tension in the string, and the accelerations of M1 and M2.

yrelhan4 · Answer

what about the force on the pulley?

vincent-lyon.fr · Answer

Apply N's 2nd law to the pulley.

yrelhan4 · Answer

the pulley is massless..

vincent-lyon.fr · Answer

Makes it even easier!

vincent-lyon.fr · Answer

If a massless body is accelerating, what will be the net force on it?

yrelhan4 · Answer

0..

yrelhan4 · Answer

@Vincent-Lyon.Fr what would i get after applying nlm to pulley?

vincent-lyon.fr · Answer

Tension in the string... and the problem is done.

yrelhan4 · Answer

i'll try .. i think i got it somewhat..

vincent-lyon.fr · Answer

It is VERY easy, not joking!

yrelhan4 · Answer

yeah.. thank you!