Question 3

Author Message   Lau Kai Kwong Username: lkk Registered: 04-2003 Posted on Sunday, April 13, 2003 - 12:32 am:    A uniform ladder rests in equilibrium with one end against a smooth vertical wall and the other end against a smooth plane inclined at 30° to the horizontal. Find the inclination of the ladder to the horizontal. Please post your solution.   971911 Username: 971911 Registered: 04-2003 Posted on Tuesday, April 15, 2003 - 10:11 pm:    in equi R2sin120=R1----1 take moment about mg R1*l*cos60=R2*l*(90-£c)---2 on solving 1&2 tan£c=sin120 £c=40.9   971911 Username: 971911 Registered: 04-2003 Posted on Tuesday, April 15, 2003 - 10:33 pm:    oh how to post the picture????????   Lau Kai Kwong Username: lkk Registered: 04-2003 Posted on Tuesday, April 15, 2003 - 11:13 pm:    See the replies in Question 1. ªá has asked this question before.   971911 Username: 971911 Registered: 04-2003 Posted on Tuesday, April 15, 2003 - 11:22 pm:      971911 Username: 971911 Registered: 04-2003 Posted on Tuesday, April 15, 2003 - 11:29 pm:      Lau Kai Kwong Username: lkk Registered: 04-2003 Posted on Tuesday, April 15, 2003 - 11:48 pm:    From your figure, there is only forces to the right direction, but no forces to the left direction. So it is not in equilibrium.   971911 Username: 971911 Registered: 04-2003 Posted on Wednesday, April 16, 2003 - 04:26 pm:    R1 =R2cos60-----1 W =R2sin 60-----2 take moment about R2 R1 * 2 Lsin £c=W * Lcos£c-----3 on solving 1,2& 3 tan£c=(tan60)/2 £c=40.9   971911 Username: 971911 Registered: 04-2003 Posted on Wednesday, April 16, 2003 - 04:28 pm:      Lau Kai Kwong Username: lkk Registered: 04-2003 Posted on Wednesday, April 16, 2003 - 06:57 pm:    Okay. But how can you take moment about a force (R2)?