Lab Report
Research Question: How does the number of rubber bands affect the force needed to pull them a certain distance?
Variables:
 The independent variable is the number of rubber bands we used for each set.
 The dependent variable is the force needed to pull the set of rubber bands 5 cm.
Control
Variables
How it could impact the
results
Method to control the variable
The type of
rubber band
used
If we don’t use the same type
of rubber band for each set
then the result might get
skewed because the some
rubber bands will be either
weaker or stronger than others.
When we make our sets of rubber band, we
made sure that the rubber bands we used
were of the same type, thickness, and size.
To make sure that the rubber bands are the
same size measure the diameter of each
one and make sure that they are
approximately the same.
Displacement of
the rubber band
(5 cm)
If we measure the force at a
different distance for each set
of rubber bands, then there will
be 2 independent variables and
our data will be skewed.
We used a measuring tape to make sure
that the rubber bands were being pulled to
the same distance for each set.
Height of the
Table
If we have fluctuating heights
for the table, than this could
result in systematic error,
because all of our
measurements might be
skewed from the actual value
We made sure to set the table at the same
height for all of the trails so that we have a
leveled surface.
Type of Spring
Scale used
Some spring scales will have
slight differences in recording
the force, therefore the force
used for each set of rubber
bands might be skewed.
We used one spring scale for all the sets of
rubber bands.
Materials:
 Spring Scale
 Rubber bands
 Measuring tape
 Scotch Tape
 Table
Procedure for the Collection of Data:
1. Gather 15 rubber bands that are the same in type, thickness, and size.
2. Make sure that the rubber bands are not longer than others because if different types are used then we will not be
able to establish that rubber bands have a cause and effect relationship with the force because different rubber
bands will affect the force needed.
3. Separate the rubber bands into 5 groups such that each group has differing numbers of rubber bands. (1 group
with 1 rubber band, 2 rubber bands, 3 rubber bands, 4 rubber bands, and 5 rubber bands)
4. Adhese the Spring Scale onto the table using the Scotch Tape, so that the surface is more stable. Use the same
spring scale for each group of rubber bands.
5. After taping the spring scale to the surface, tape the measuring tape to the surface of the table as well.
6.
7.
8.
9.
Attach the first set of rubber bands onto the spring scale
Mark where the rubber bands are when not being pulled and measure 5 cm away from its position so that you
will know when to record the force.
Proceed to stretch the rubber band(s) 5 cm and record the force.
Repeat procedure 7 and 8 for the remaining rubber band groups
Data:
Number of rubber bands used
Force (Newtons)
1 rubber band
3.2 ± 0.2 N
2 rubber bands
5.8 ± 0.2 N
3 rubber bands
7.8 ± 0.2 N
4 rubber bands
9.4 ± 0.2 N
5 rubber bands
10.8 ± 0.2 N
Graph:
*Note* The reason why there are vertical, not horizontal values of Error Bars is because the Number of Rubber Bands are
a positive set value, not a value that can contain negative or decimal values
Conclusion: Our data showed that as the number of rubber bands increased, the force needed to pull the set 5 cm
increased as well. However, as the number of rubber bands increased, the force needed increased to a less extent with each
rubber band addition. We found that the amount of rubber bands has a relation with the force needed to stretch the rubber
band up to 5 cm to a certain extent. This is because according to our data, the force is not directly proportional to the
number of rubber. Therefore, we can’t conclude that the number of rubber bands causes an increase in force needed. Our
data might have a few inaccuracies or overlooking in terms of measuring. Here are the Errors or things to consider for :
Errors
Explanation
Data might not be accounted
for more than 5 rubber bands
This lab only considers upto 5 trials. This model won’t be
accurate for values more than 5 rubber bands since rubber bands
are discrete values.
Parallax(Systematic Error)
Praharsha might have viewed the meniscus of the Spring Scale
different than Barath because they both were looking at it
through different angles. This would indicate that we might not
be calculating accurate values, but we keep on getting values
with the same amount of uncertainty for each trial
Incomplete Definition
(Random Error)
Praharsha might have stretched the rubber band differently
compared to Barath.
Failure to calibrate
instrument (Spring Scale) to
zero (Systematic Error)
The meniscus was sometimes below the zero of the instrument.
This would lead to precise, not accurate values.
Factors Failed to be Accounted For:
1. Material of Rubber Band
2. Tension that might be in relation to the different type of material for the rubber band
3. The amount of Force needed to pull the hook of the Spring Scale down in order to commence measurements
Environmental Factors(Systematic or Random)
1. Vibration of table during experiment, which was caused by surrounding movement of other experimenters
2. Inconsistencies with Room Temperature
Evaluating Procedure:
Errors: During the experiment we might have had errors with the measuring tape. When we measured 5 cm during the
experiment, the measuring tape was not straightened out properly, which could have led to measurement errors. Also
during the procedure, we did not set a defined way to stretch the rubber band. Therefore we stretched the rubber bands a
different way for some of the sets and could have affected our results.
Weaknesses:
 A weakness of our procedure is the spring scale. When we used the spring scale, we observed that when there
was nothing attached to the hook, the scale read 0.2 Newtons rather than 0. As a result of this weakness we might
not have been able to measure accurately.

Another weakness would would have been the lack of distinguishment of tasks for each member. Both members
of the experiment were doing the same tasks throughout the experiment, like measuring the Force, pulling the
rubber band(s), and/or noting down the values. As a result, this would contribute to a lot of systematic and
random errors because each lab member might interpret each thing differently, such as the place of the meniscus
or different method of pulling rubber band.
Aspects to improve on the Investigation:
Our experiment was more precise compared to accurate, because our experiment contained more Systematic
Errors compared to Random Errors. Therefore, our experiment would be reproducible in the sense that this new
experiment would produce similar values, but it might not be the accepted or the true value that should be represented.
One way we could reduce the Random Error in the experiment might be through having one person conduct the
experiment, and note the values, and the other person note down the values, so that there would be more consistency with
producing accurate values and still getting precision
One way to improve the Systematic Error in the experiment might be the same way we have improved on reducing
random errors: make one person conduct the experiment. That way we reduce the chances of parallax. Additionally, we
could have had better and more updated equipment and tools of measurement because our meniscus was a a little bit
skewed for some trials because the Spring Scale was not properly calibrated to zero for some trials. In addition, there
should be more control of variables, like surrounding movement and temperature, so that it might not have a tendency to
influence our results.