# Homework Help: Mass of dresser?

1. Apr 1, 2016

### gmichel395

1. The problem statement, all variables and given/known data
"Using the pulley system shown to lift the heavy dresser, the person is applying a force of 150N to the end of the rope. Which of the following is closest to the maximum mass of the dresser that can be lifted with this force? [Ignore weight & friction from pulleys/rope.]"

A) 46kg
B) 92kg
C) 110kg
D) 150kg
E) 180kg

2. Relevant equations

Newton's 2nd & 3rd laws

3. The attempt at a solution
So she's pulling with 150 N and there are three pulleys connected to the dresser, so her effort is tripled. 450N lifts the dresser and so the mass is 46kg?

2. Apr 1, 2016

### Staff: Mentor

Label each section of the rope with its tension. How many sections of rope are supporting the dresser?

3. Apr 1, 2016

### gmichel395

I count six sections plus the one the girl is holding so seven. 7*150 divided by g gives approximately 110kg?

4. Apr 1, 2016

### Staff: Mentor

The one the girl is holding is holding the girl...not the dresser. So one less. You want to count only the ropes that are directly supporting the load.

5. Apr 1, 2016

### gmichel395

Ah so six. And the answer is 92kg?

6. Apr 1, 2016

Yes.