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Name: _________________________
Block: ________
Date: ____________
Newton’s Second Law: The acceleration of an object is directly proportional to the net force applied, and
inversely proportional to the mass.
Purpose: In this lab, we will observe, more or less quantitatively, the relationships between force,
mass, and acceleration. Using the MacBook computers and motion detectors we will be attempting
to validate Newton’s second law.
Motion
detector
m
Part I: The effect on Acceleration when you change the Force:
Goal: Observing the relationship between force applied and acceleration produced.
In this part of the lab, you will vary the Force by changing the weight hanging over the edge of the
table. For each trial, you will use a different amount of suspended (hanging) mass. Using the
formula W=mg, you can calculate the force (weight) that is doing the pulling. For these calculations,
m is the mass of the hanging masses, and g is the acceleration due to gravity, 9.81 m/s2.
1. Write a prediction related to what you expect to observe as you increase the force (the hanging
weight) that is causing the acceleration.
2. Fill in the following table using the following equations for your calculations:
Weight: Fg = mhang ´ g , where mhang = hanging mass and g = 9.81 m/s2
Acceleration: acalc 
Fnet
, where Hanging Weight is the Net Force and
mcart
mtotal = mass of the empty cart + hanging mass, 0.500kg.
Show your work (USE GUIDE) on a separate sheet of paper, which will be collected with the lab:
mhang
Fg = mhang ´ g
mtotal
.01 kg
.500 kg
.02 kg
.500 kg
.04 kg
.500 kg
acalc =
Fg
mtotal
aobserved = slope of
v-t graph
3. For each trial, use the logger pro program to measure the acceleration by using the analyze
function to find the slope of the velocity vs. time graph. Add these numbers to the table above in the
aobserved column.
Part II: The effect on Acceleration when you change the Mass:
Goal: Observing the relationship between the mass accelerated, and the acceleration produced.
In this part of the lab, you will vary the mass of the cart, keeping the suspended mass constant, and
observe (record) the acceleration of the cart. To determine the total mass being accelerated you must
include the mass of the cart and any additional mass on the car.
1. Write a prediction about what you will observe in the acceleration as you change the mass of the
cart that is being accelerated.
2. Fill in the table using the following equations for your calculations:
Weight: Fg = mhang ´ g , where mhang = 0.04 kg (40 grams) and g = 9.81 m/s2
Acceleration: acalc 
Fnet
, where Hanging Weight is the Net Force and
mcart
mtotal = mass of the empty cart + hanging mass.
Show your work (USE GUIDE) on a separate sheet of paper, which will be collected with the lab:
mhang
Fg = mhang ´ g
mtotal
.04 kg
0.250 kg + .04kg
.04 kg
0.500 kg + .04kg
.04 kg
1.000 kg + .04kg
acalc =
Fg
mtotal
aobserved = slope of
v-t graph
3. For each trial, use the logger pro program to measure the acceleration by using the analyze
function to find the slope of the velocity vs. time graph. Add these numbers to the table above.
Write or Type the analysis and conclusion on a separate sheet of paper. Make sure you (1) Use
COMPLETE SENTENCES and (2) include the QUESTIONS in your answers so the reader DOES NOT have to refer back
to the questions.
Analysis:
For part I and II of the lab:
1. Comment on any differences you saw between the acceleration you calculated and the
acceleration you measured with the motion sensor.
2. If there were differences, what may have caused them?
3. What types of error might be present in this experiment?
Conclusion: (Should be written using C.E.R format)
How well does your data agree with Newton’s second law? Was your observed acceleration
consistent with what you expected?
• For Part I, did you observe a directly proportional relationship (e.g. did 2x the Force produce
2x the acceleration?)
• For Part II, did you observe an inversely proportional relationship (e.g. did 2x the mass
result in 1/2 the acceleration?)
C.E.R Template to use for writing your conclusion.
Question: How well does your data agree with Newton’s second law? Was your observed
acceleration consistent with what you expected?
Claim:
Write a statement that answers the following question: How well does your data agree with Newton’s 2nd Law? Was your
observed acceleration consistent with what you expected?
Evidence:
Provide sufficient and appropriate data to support your claim. Make sure you include:
a.
Data from Part I. (Refer and summarize the data in your own words. You may use this sentence starter “According to
the data I collected in part I, as the Force increases from _____ to ______, the acceleration…while the mass of
the whole system stays at a constant _______. )
b.
Data from Part II. (Refer and summarize the data in your own words. You may use this sentence starter “According
to the data I collected in part II, as the mass of the cart increases from ______ to ______, the acceleration…while
the force used to accelerate the system stays at a constant ________.
c.
Compare your calculated data to the observed data for acceleration from Part I and Part II.
Reasoning:
Explain how the data supports your claim. Make sure you include:
a.
Restate Newton’s 2nd Law of Motion, explain the equation.
b.
Explain what directly proportional and inversely proportional relationship applies to the variables in Newton’s 2 nd Law of
Motion.
c.
For Part I, did you observe a directly proportional relationship?
d.
For Part II, did you observe an inversely proportional relationship?
e.
Was the observed data consistent with the predicted (calculated) data? Why or Why not?