PHYS 2101

1
PHYS 2101
Fall 2009

• Static Equilibrium

2
PHYS 2101
Fall 2009
CT1
The figure below shows the overhead views of a
series of uniform rods on which forces act
perpendicularly to the rod. If the magnitudes of
the forces are adjusted properly (but kept
non-zero), which of the rods can be in static
equilibrium?
1
2
3
4
5
6
3
PHYS 2101
Fall 2009
CT2
A uniform beam of length L and mass M 1.8 kg is
at rest on two scales. A uniform block with mass
m 2.7 kg is at rest on the beam, with its
center a distance L/4 from the beams left end.
Which scale will read a larger value? 1 - The
scale on the left end of the beam 2 - The scale
on the right end of the beam 3 - Both scales
will read the same weight
4
PHYS 2101
Fall 2009
EX1
A uniform beam of length L and mass M 1.8 kg is
at rest on two scales. A uniform block with mass
m 2.7 kg is at rest on the beam, with its
center a distance L/4 from the beams left end.
What do the scales read?
5
PHYS 2101
Fall 2009
EX2
A diver of weight 500 N stands at the end of a
diving board of length L 4 m and negligible
mass. The board is fixed to two pedestals
separated by distance d 1.5 m. What are the
magnitudes and directions of the forces exerted
on the board by the two pedestals?
6
PHYS 2101
Fall 2009
EX3
A uniform ladder of length L 12 m and mass m
15 kg leans against a frictionless wall at an
angle of 30 with the wall. A firefighter of
mass M 72 kg climbs the ladder until he is at a
point L/3 from the top of the ladder. What are
the magnitudes of the forces on the ladder from
the wall and ground?
7
PHYS 2101
Fall 2009
EX4
A uniform beam of 200 kg is fastened to a wall
with a hinge on one end and a cable that can
withstand a maximum tension of 2500 N. The angle
between the cable and the beam is 30. If you
weigh 200 N, how far can you safely walk along
the beam away from the wall?
8
PHYS 2101
Fall 2009
EX4
A 1200 N uniform beam is attached to a vertical
wall at one end and is supported by a cable at
the other end. A W 2000 N crate hangs from the
far end of the beam. Calculate the tension in
the cable connected to the wall and the force
exerted by the wall on the beam.
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PHYS 2101
Fall 2009
CT3
Can any of the rods be in static equilibrium?
1
2
3
10
PHYS 2101
Fall 2009
CT3
Where can F2 be if the rods are in static
equilibrium?
1
2
3
11
PHYS 2101
Fall 2009
CT4
What was the real concern with the Leaning Tower
of Pisa? A - It would fall over. B - One side
of the structure would crumple.