(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

An 80.0 kg student stands on a 20.0 kg platform and applies a steady downwards force of 300 N on a long rope; the rope extends up from the students hands passes over pulley#1 at the top and then under pulley #2; finally the rope is attached to the bottom of pulley #1, as shown in the figure. Assume that the ropes and pulleys have negligible mass and that the pulleys are ideal and frictionless. The top pulley remains at rest.

2. Relevant equations

See figure.

3. The attempt at a solution

I tried doing the weight of the student which equals 784 N - the force (300 N) = 484.

However, the correct answer is 420... I do not know how to arrive at that value.

Another similar problem:

Need to find the normal force which the platform exerts on the student's feet:

My attempt same as first problem: 784 N - 160 = 624.

However, the correct answer is 480 N.

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Pulleys and Normal Force

**Physics Forums | Science Articles, Homework Help, Discussion**