PASCO ME-8569 DENSITY SET - Manual (Page 12)

scientific 8
012-04774A
Thus the buoyant force can be calculated by finding the
difference between the weight of the object in air and the
apparent weight of the object when it is submerged in water.
1. Put the triple-beam balance on top of a stand as shown in
Figure 3. Tie a string to the bottom of the pan.
2. Hang the first object from the string. The balance will
read the same as when the object is placed on top of the pan.
Multiply the mass by the acceleration due to gravity
(9.8 m/s
2 ) and record the object’s weight in Table 3.2.
Buoyant
Force
Weight in
water
Weight in
air
Figure 2: Free Body Diagram
5. Calculate the mass of the water by subtracting the mass of
the beaker. Then calculate the weight of the displaced water
by multiplying by the acceleration due to gravity (9.8 m/s
2 ).
Record the result in Table 3.1 and Table 3.2.
6. Repeat this procedure for the other objects. Note that the
plastic object will float in water but it can still be used in this
part of the experiment. Also, repeat the procedure for the
brass cylinder with only half the cylinder submerged.
II. UPWARD FORCE
When an object is submerged in a fluid, the apparent weight
of the object is less than the weight in air because of the
buoyant force (See Figure 2).
30 40 50 60 70 80 90 100g
1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 g
SCALE
Figure 3: Scale Setup
OBJECT
WEIGHT
IN AIR
WEIGHT IN
WATER
BF =
W -W
WEIGHT OF
DISPLACED WATER
AL. CYLINDER
AL. BLOCK
BRASS CYL.
BRASS BLOCK
PLASTIC CYL.
AL. IRREG. SHAPE
BRASS CYL. 1/2
SUBMERGED
AIR WATER
Table 3.2: Measurements