Crate being pulled at angle, find tension

  • #1
Hello,

I'm new to physics forums, so excuse me ahead of time if something is wrong.


Homework Statement



A warehouse employee drags a 72 kg wooden crate across the floor at a constant velocity by pulling on a strap attached to the bottom of the box. The crate is tiled 25° above the horizontal, and the strap is inclined 61° above the horizontal. The center of gravity of the box coincides with its geometrical center, as indicated in the drawing. Find the magnitude of the tension in the strap.

The dimensions of the crate are .4m by .9m.
The .9m length is the side that is 25 degrees above the horizon.



Homework Equations



F(weight)=mg

T=rsin(theta)F?

The Attempt at a Solution



Its weight is 705.6N

705.6Ntan(25)=329.02N which is the force pulling the crate

this would translate into the x component of the tension.

329.02N/cos(61)= 678.65N

I'm not sure if/how to use torque or if torque affects the system at all.
I'm pretty sure that this problem isn't as simple as I made it out to be.
Thanks for your help!
 
Last edited:

Answers and Replies

  • #2
gneill
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Its weight is 705.6N

705.6Ntan(25)=329.02N which is the force pulling the crate
How did you arrive at that conclusion?

~[snip]~
I'm not sure if/how to use torque or if torque affects the system at all.
I'm pretty sure that this problem isn't as simple as I made it out to be.
Thanks for your help!
Yes, you'll need to use torques in order to determine the component of the tension that's keeping the crate's end suspended above the floor. The crate is pivoting along the bottom edge where it touches the floor. Find the torques due to the strap tension at the raised end of the box and due to gravity acting through the center of mass.
 

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