PRESANTATION SEE-SAW

SEE-SAW

A hanging flower basket having weight, W2 =23 N is hung out
over the edge of a balcony railing on a uniform horizontal beam
AB of length 110 cm that rests on the balcony railing. The basket
is counterbalanced by a body of weight, W1 as shown in Figure 1.
If the mass of the beam is 3.0 kg, calculate

a. the weight, W1 needed,
b. the force exerted on the beam at point O.

A 35 cm O 75 cm B

W2 W1

Figure 1



A 0.35 m 0.20 m B
0.75 m
2 1
CG

O

0.55 m m റ 0.55 m

A see-saw consists of a uniform board of mass 10 kg and
length 3.50 m supports a father and daughter with masses
60 kg and 45 kg, respectively as shown in Figure 2. The
fulcrum is under the centre of gravity of the board.
Determine

a. the magnitude of the force exerted by the fulcrum on

the board,

b. where the father should sit from the fulcrum to balance

the system.

Figure 2

A uniform ladder AB of length 10 m and mass 5.0 kg leans against
a smooth wall as shown in Figure 3.The height of the end A of
the ladder is 8.0 m from the rough floor.

a. Determine the horizontal and vertical forces the floor exerts
on the end B of the ladder when a firefighter of mass 60 kg is 3.0
m from B.

b. If the ladder is just on the verge of slipping when the firefighter
is 7.0 m up the ladder , Calculate the coefficient of static friction
between ladder and floor.

A

smooth
wall B

rough floor

Figure 3

A

α
β

8.0 m CG 10 m

β 3.0 m
B
5.0 m βα

6.0 m

A floodlight of mass 20.0 kg in a park is supported at the end of
a 10.0 kg uniform horizontal beam that is hinged to a pole as
shown in Figure 4. A cable at an angle 30 with the beam helps to
support the light.

a. Sketch a free body diagram of the beam.

b. Determine

i. the tension in the cable,

ii. the force exerted on the beam by the pole.

Figure 4

റ
O
30
0.5l
CG

റ

l

റ

A traffic light hangs from a structure as show in Figure 5.
The uniform aluminum pole AB is 7.5 m long has a mass
of 8.0 kg. The mass of the traffic light is 12.0 kg.
Determine

a. the tension in the horizontal massless cable CD,

b. the vertical and horizontal components of the force
exerted by the pivot A on the aluminum pole.

Figure 5