# Need help getting started..

• Oct 27th 2010, 01:37 PM
Need help getting started..
Sled of 196 N is being pulled across a horizontal surface at a constant velocity. So it's in equilibrium right??
The pulling force(Tension force?) has a magnitude of 80 n and is direct at an angle 30degree above the horizontal. Determine the coefficient of the kinetic friction.

I am stuck on drawing the FBD. I suck at those. I get them confused.
Need help on getting started, thanks.

So 30 degree angle from the 0degree, Force of 80 is perpendicular to that, so at 120 degrees?? Where do I put the Ff? to figure out the u
• Oct 27th 2010, 02:45 PM
TheEmptySet
Quote:

Sled of 196 N is being pulled across a horizontal surface at a constant velocity. So it's in equilibrium right??
The pulling force(Tension force?) has a magnitude of 80 n and is direct at an angle 30degree above the horizontal. Determine the coefficient of the kinetic friction.

I am stuck on drawing the FBD. I suck at those. I get them confused.
Need help on getting started, thanks.

So 30 degree angle from the 0degree, Force of 80 is perpendicular to that, so at 120 degrees?? Where do I put the Ff? to figure out the u

Here is the free body diagram

Attachment 19497

$\displaystyle \sum F_x=80\cos(30^{\circ})-\mu_k\eta=ma_x=0$

$\displaystyle \sum F_y=\eta+80\sin(30^{\circ})-196=ma_y=0$
• Oct 27th 2010, 03:01 PM
Solve for eta $(\eta)$ the normal force in the 2nd equation.
Sub this into the first equation and solve for the coefficient of kinetic friction $\mu_k$