- #1
Zynoakib
- 70
- 0
Homework Statement
Sir Lost-a-Lot dons his armor and sets out from the
castle on his trusty steed (Fig. P12.19). Usually, the
drawbridge is lowered to a horizontal position so that
the end of the bridge rests on the stone ledge. Unfortunately,
Lost-a-Lot’s squire didn’t lower the drawbridge
far enough and stopped it at 20 degree above
the horizontal. The knight and his horse stop when
their combined center of mass is 1.00 m from the
end of the bridge. The uniform bridge is 8.00 m
long and has mass 2 000 kg. The lift cable is attached
to the bridge 5.00 m from the hinge at the castle end
and to a point on the castle wall 12.0 m above the
bridge. Lost-a-Lot’s mass combined with his armor
and steed is 1 000 kg. Determine the tension in the
cable
Homework Equations
The Attempt at a Solution
Actually I have the answer, but I just don't understand why you have to take the horizontal component of tension and the force from the hinge because it is perpendicular to surface of the bridge
The angle between the wall and the cable is 24.5 degrees
Take torques about the hinge end of the bridge:
Hx (0)+ Hy (0)− Mg(4.00 m)cos20.0°
− (T sin 24.5°)(1.71 m)+ (T cos24.5°)(4.70 m)
− mg(7.00 m)cos20.0° = 0
T = 27.7 kN
Thanks