# Can a person hanging from a rope pull the person holding the rope up?

1. Jan 11, 2012

### patriots51

1. The problem statement, all variables and given/known data

A rope of negligible mass passes over a pulley of negligible mass attached to the ceiling. One end is held by student A (70 kg) who is at rest. The other side has student b (60 kg).

I need to explain why or why not student b can lift student a off of the ground if he accelerates up the rope, increasing tension.

2. Relevant equations

the force of student A is 700 N (70kg x 10 m/s^2)
the force of student B is 600 N (60kg x 10m/s^2)
the normal force exerted on student A by the floor is 100N (?)
the force of tension will vary depending on student B's acceleration (F=ma)

3. The attempt at a solution

I don't believe that it would be possible to pull the person holding the rope up, but i'm not sure how to prove it.

2. Jan 11, 2012

### SammyS

Staff Emeritus
Hello patriots51. Welcome to PF !

If you were told that it is possible for student B to lift student A off of the ground, could you explain how it's possible?

3. Jan 12, 2012

### Staff: Mentor

To demonstrate "lifting off the ground" B just needs to momentarily cause A's feet leave the floor.