ANSWER KEY
EXPERIMENT 5: ARCHIMEDES’ PRINCIPLE
OBJECTIVE
To determine the buoyant force from Archimedes’ Principle.
INFERENCE
Archimedes` Principle states that “When an object is immersed in a fluid (liquid or
gas), the buoyant force (up thrust force) on the object is equal to the weight of
fluid displaced by the object”.
HYPOTHESIS
The buoyant force on an object is equal to the weight of the water displaced.
APPARATUS
1. Retort stand
2. Spring balance / Balance
3. 3 Set of Block (Wood, Metal, Plastic)
4. Beaker
5. Eureka beaker
6. Scissor
7. String
-1
-1
-1
-2
-1
-1
PROCEDURES
1.
Weigh the mass of empty beaker.
2.
Hang the spring balance at the arm of retort stand.
3.
Tie the wooden block and hang to the spring balance.
4.
Record the weight of the block in the air as Figure 5a.
5.
Fill the Eureka beaker with water.
6.
Set the apparatus as Figure 5b.
7.
Then, lower the arm of the retort stand tied with the block gently.
8.
Let the block arise/sink in water.
9.
Record the weight of the block.
10.
Water will be displaced from eureka beaker into the other beaker.
11.
Record the mass of the displaced water in the beaker.
12.
Repeat the above procedures by using the plastic and metal blocks
1
No
1
Criteria
Procedures
Excellent
(4 marks)
Procedures are
clearly
described in
complete and
passive
sentences.
Steps are also
numbered.
Good
(3 marks)
Procedures
are clearly
described in
complete and
active
sentences.
Steps are
also
numbered.
Needs
Improvement
(1 mark)
Unsatisfactory
(0 mark)
Procedures
are partially
stated and
difficult to
follow.
Procedures
are not stated.
Satisfactory
(2 marks)
Needs
Improvement
(1 mark)
Unsatisfactory
(0 mark)
Diagrams are
included and
partially labeled.
Diagrams are
included but
are not
labeled
Needed
diagrams are
missing.
Satisfactory
(2 marks)
Procedures are
stated but difficult
to follow.
DIAGRAM
Figure 5a
No
2
Criteria
Drawings
/Diagrams
Excellent
(4 marks)
Clear, accurate
diagrams are
included.
Diagrams are
labeled neatly
and accurately.
Figure 5b
Good
(3 marks)
Diagrams are
included and
are labeled.
2
DATA
a.
Mass of empty beaker = 95.67 g
Wood
1.0
0.0
194.17
0.94
Significa
nt loss
of block
weight
FB = T1T2
1.0
Plastic
1.6
0.2
232.41
1.34
1.4
4.28
Metal
4.95
3.25
260.96
1.62
1.7
4.7
Weight
of Water
displace
d (N)
Average
Mass of
beaker
with
displaced
water (g)
Weight of Block (N)
Type of
Block
In the air T1 (N)
Trial 1
1.
Trial 2
Average
In the water T2 (N)
Trial 1
Trial 2
%
Error
6.0
Weight of water = Mass of beaker with displaced water – mass of empty beaker.
i. Wood = 194.17g – 95.67g = 95.5g
ii. Plastic = 232.41g – 95.67g = 136.74g
iii. Metal = 260.96g – 95.67g = 165.29g
2.
Convert the answer in gram (g) to kilogram (kg)
i. Wood = 95.5 / 1000 = 0.0955 kg
ii. Plastic = 136.74 /1000 = 0.13674 kg
iii. Metal = 165.29/1000 = 0.16529 kg
3.
Convert the answer in kg to Newton ( N ) by multiply 9.81 kg/ms2
i. Wood = 0.0955 x 9.81 = 0.94 N
ii. Plastic = 0.13674 x 9.81 = 1.34 N
iii. Metal = 0.16529 x 9.81 = 1.62 N
4.
Significant loss of block weight (FB=T1-T2) = Weight of the block in the air, T1 –
weight of block in the water T2.
i. Wood = 1.0N – 0.0N= 1.0N
ii. Plastic = 1.6N – 0.2N = 1.4 N
iii. Metal = 4.95 N – 3.25 N = 1.7 N
3
5.
To find the error: Error percentage should be less than 10%
Percent Error:
( | theoretical - actual | / theoretical) x 100
(same as 100 - % yield)
Error (%) =
Wood =
Metal =
3
4
Significant loss of block weight,FB
1.0−0.94
Plastic =
No
Significant loss of block weight,FB – Weight of water displaced
Criteria
Data
Calculations
1.0
𝑥 100= 6%
1.4−1.34
1.40
1.7−1.62
1.7
𝑥 100= 4.28%
𝑥 100= 4.7%
Excellent
(4 marks)
Good
(3 marks)
Satisfactory
(2 marks)
Presentation of
the data in
tables or graphs
is done correctly
and accordingly.
Graphs and/or
tables are
labeled and
titled.
Accurate
presentation
of the data in
tables or
graphs.
Graphs
and/or tables
are not
labeled and
titled.
Accurate
presentation of
the data in written
form, but no
graphs or tables is
presented.
All calculations
are shown and
the results are
correct with
appropriate units.
All
calculations
are shown
and the
results are
correct
without
appropriate
units.
All calculations
are shown but not
all the results are
correct.
Needs
Improvement
(1 mark)
Data are shown
but inaccurate.
All
calculations
are shown
but all the
results are
incorrect
Unsatisfactory
(0 mark)
Data are not
shown.
No
calculations
are shown.
4
ANALYSIS
i)
ii)
iii)
iv)
v)
No
5
An object will float if the buoyant force is greater than the weight of the
object.
An object will sink if its weight is greater than the buoyant force.
From the experiment, metal has a greater buoyant force for it to float.
Random error from equipment such as eureka beaker and spring balance.
Error from student (human error) by using their finger to push the object to
immerse in the fluid.
Criteria
Analysis
Excellent
(4 marks)
Explain the
findings in the
experiment. Able
to explain
experimental
errors, their
possible effects,
and ways to
reduce errors.
Good
(3 marks)
Explain the
findings in the
experiment.
Able to explain
experimental
errors and their
possible
effects.
Satisfactory
(2 marks)
Needs
Improvement
(1 mark)
Unsatisfactory
(0 mark)
Explain very
briefly about the
findings in
experiment.
Experimental
errors are
mentioned.
Explain very
briefly about the
findings in
experiment Or
only
experimental
errors are
mentioned.
No analyses are
shown.
QUESTIONS
1. Why do some objects;
a. float when placed in water
An object will float if the buoyant force is greater than the weight of the
object.
b. sink when placed in water
An object will sink if its weight is greater than the buoyant force.
2. From the experiment, which block has a greater buoyant force for it to float?
From the experiment, metal has a greater buoyant force for it to float.
No
6
Criteria
Questions
Excellent
(4 marks)
The questions
answered are
correctly, clearly
identified and
stated according
to the theory.
Good
(3 marks)
The questions
answered in
the lab report
is identified,
but not stated
according to
the theory.
Satisfactory
(2 marks)
Not all the
questions
are answered.
Needs
Improvement
(1 mark)
Unsatisfactory
(0 mark)
The
questions
answered in
the lab report
are
irrelevant.
The questions
are not
answered.
5
CONCLUSION
From the experiment, it is found that when an object is immersed in water, the
buoyant force (up thrust force) on the object is equal to the weight of water
displaced by the object.
No
7
Criteria
Conclusion
Excellent
(4 marks)
Conclusion
included the
finding from the
experiment and
supported the
hypothesis /
theory.
Good
(3 marks)
Conclusion
included the
finding from the
experiment but
supported with
incorrect
hypothesis /
theory.
Satisfactory
(2 marks)
Conclusion
included the finding
from the
experiment but not
supported the
hypothesis / theory.
Needs
Improvement
(1 mark)
Unsatisfactory
(0 mark)
Conclusion
included but not
related to the
experiment.
No conclusion
was included in
the report.
6