# Homework Help: Newton's laws- pulleys

1. Sep 30, 2008

### crhscoog

1. The problem statement, all variables and given/known data
http://img213.imageshack.us/img213/6969/physicsproblemhq3.png [Broken]

A rope of negligible mass passes over a pulley of negligible mass attached to the ceiling as shown above. One end of the rope is held by Student A of mass 70 kg, who is at rest on the floor. The opposite end of the rope is held by Student B of mass 60 kg, who is suspended at rest above the floor.

1. Calculate the magnitude of the force exerted by the floor on Student A.

2. Student B now climbs up the rope at a constant acceleration of .25 m/s^2 with respect to the floor. Calculate the tension in the rope while Student B is accelerating.

3. As Student B is accelerating, is Student A pulled upward off the floor? Justify your answer.

4. With what minimum acceleration must Student B climb up the rope to lift Student A upward off the floor?

3. The attempt at a solution

1. Because it is at rest:
T + N = Mg, or N = Mg - T = (70 - 60)g ~ 98 N

I am currently doing 2-4 right now... I'll post what I get after I finish them.

Last edited by a moderator: May 3, 2017