clarineterr
Jul11-09, 11:41 PM
1. The problem statement, all variables and given/known data
A window washer of mass M is sitting on a platform suspended by a system of cables and pulleys as shown . He is pulling on the cable with a force of magnitude F. The cables and pulleys are ideal (massless and frictionless), and the platform has negligible mass.Find the magnitude of the minimum force F that allows the window washer to move upward.
Express your answer in terms of the mass M and the magnitude of the acceleration due to gravity g.
http://i943.photobucket.com/albums/ad277/clarineterr/MFS_1l_18_001.jpg
2. Relevant equations
Newton's second Law
3. The attempt at a solution
For the person: Ma = F + T -Mg where T is the tension in the cable holding the platform and F is the force of the rope on the washer.
Then from the lower washer T = 2T_{1}, where T_{1} is the tension in the rope
So Ma = F + 2T_{1} - Mg
The block is about to move so Ma = 0 and I think T_{1}=F so then
0 = 3F - Mg
I am not sure about this though
A window washer of mass M is sitting on a platform suspended by a system of cables and pulleys as shown . He is pulling on the cable with a force of magnitude F. The cables and pulleys are ideal (massless and frictionless), and the platform has negligible mass.Find the magnitude of the minimum force F that allows the window washer to move upward.
Express your answer in terms of the mass M and the magnitude of the acceleration due to gravity g.
http://i943.photobucket.com/albums/ad277/clarineterr/MFS_1l_18_001.jpg
2. Relevant equations
Newton's second Law
3. The attempt at a solution
For the person: Ma = F + T -Mg where T is the tension in the cable holding the platform and F is the force of the rope on the washer.
Then from the lower washer T = 2T_{1}, where T_{1} is the tension in the rope
So Ma = F + 2T_{1} - Mg
The block is about to move so Ma = 0 and I think T_{1}=F so then
0 = 3F - Mg
I am not sure about this though