Physics
posted by Steph .
A 10kg ladder 2.5m long rests against a frictionless wall with its base on the floor 80cm from the wall. How much force does the top of the ladder exert on the wall?

This question has been answered by Damon
http://www.jiskha.com/display.cgi?id=1303587287
The moment of the ladder about the floor support point is zero. The 98 N ladder weight acts downward 0.4 m from the wall.
The wall contact point is sqrt[2.5^20.8^2] = 2.37 m above the floor. The force F at the wall contact point is normal to the wall, because it is frictionless there.
Setting the total moment equal to zero,
98*0.4 = F*2.37
F = 16.54 N