r\ +
-. v
l) Bent see-saw
(25 points)
The see-saw
shown
at
the right consists of a triangular base
and
a bar
with a 90o
bend 2 m from the pivot point on its
right side. A point-like 10 kg mass sits
atop the bent arm of
the see-saw bar at a position that is at an angle of30o above
the horizontal from the
pivot point. A point-like 3 kg weight
rests
on the left side
of the see-saw 3 m from the pivot point.
The see-saw
is prevented
from rotating from its horizontal
orientation by a rope
tied to a point I m to the left of the
pivot point; the other
end
of the rope is tied to a point on the
ground directly below the point where it is tied to the see-
saw
bar. Assume
that the see-saw bar itself is massless
and
not rotating (in other
words,
it is static).
Make a free body diagram
of the see-saw
bar. Make sure to clearly label all forces.
What is the torque on the see-saw
bar about the pivot point due to the mass
on the
right? Use
the convention that clockwise torques are
positive.
What is the torque
on the see-saw bar about the pivot point due
to the mass
on the
left? Please check
your signs.
Find the tension
in the
rope.
What is the largest mass, M3, that could be added to the bar 1.5 m to the left of the
pivot point without causing the bar to rotate
counterclockwise?
a)
b)
c)
d)
e)
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