Homework Help: Confusing static equilibrium problem

1. Dec 8, 2004

barnsworth

static equilibrium problem

A 900-N boy sits on top of a ladder of negligible weight that rests on a frictionless floor as in http://m.domaindlx.com/barnsworth/physics.JPG. There is a cross brace halfway up the ladder, and the angle at the apex is 30 degrees.

a) What is the force exerted by floor on each leg of the ladder?

b) Find tension in the cross brace.

The first part was simple enough i guess. i did 4F = 900 since net Fy = 0, giving me F = 225 for (a).

Haven't the slightest clue on part (b) though. I don't know where to begin.

Anyways, thanks for any help in advance.

Last edited by a moderator: Apr 21, 2017
2. Dec 9, 2004

Galileo

Hint: The floor exerts a normal force upwards, which creates a torque about the apex.

3. Dec 9, 2004

marlon

Also, you can calculate the length of the cross Brace using trigoniometry...

then apply the nice hint of Galileo when calculating the torque...

regards
marlon