Freebody Diagram for Crate Lifted with Steel Cable at Decreasing Speed

[homevolend]

Homework Statement

A crate is being lifted by a steel cable at a decreasing speeed. Label everything in the diagram.

The Attempt at a Solution

[PLAIN]http://img163.imageshack.us/img163/5764/drawk.png

This is what I did but it is wrong, how would I draw it to show the decreasing speed and also the lifted part?

 

[PhanthomJay]

the crate (the lifted part) is being lifted up...there's nothing going on in the horizontal direction, so those horizontal forces don't belong there. The vertical ones are OK, although usually the force you have labeled F_N is usually called F_T or just T, because it is a tension force pulling away from the crate. That's all you need to do in a free body diagram. Taking into account the decreasing speed would be asked for as a 'part b' question.

 

[homevolend]

Ok thanks, I understand. Since there is no labeled horizontal forces I don't need the Fa and Ff.

But since its being lifted isn't there an Fa or is it just FT.

 

[PhanthomJay]

Ok thanks, I understand. Since there is no labeled horizontal forces I don't need the Fa and Ff.

But since its being lifted isn't there an Fa or is it just FT.

That is right, the applied force is the tension force, in this problem. Don't put in 2 forces at the top, just the one. Here's a tip...when you draw free body diagrams, you note and label the forces acting on the object, and their direction. There are basically 2 general types of forces : action at a distance forces (like gravity forces (weight) or magnetic forces); and so called 'contact' forces, where there has to be contact with the object in order for there to be a force. Contact forces include friction forces, tension forces, spring forces, normal forces, applied pushing or pulling forces, etc.