Newton's Second Law Lab (Part A: Force)
Investigative Question:
How will increasing the pulling force on a cart affect its acceleration?
Hypothesis:
in your journal
(If…then…because…)
If we increase the mass of the cart then __(predicted result)_ because _(logical reason)__
Materials:
meter stick, cart, mass set, ~1.0 m long string, stopwatch, pulley, masking tape, spring scale
40 cm
60 cm
This time, the mass of the cart will be kept the same. All you will do is change the mass on the hanging end of
the string. increasing the pulling force on the cart.
1. Check out your lab kit from the teacher, then set up your cart as shown in the picture above. Loop
one end of the string around the end of your cart. Tie a small loop on the other end to hold masses.
2. Measure 60 cm from the end of the table and place a piece of tape there. This is where you the front
end of your cart will start. Place a second piece of tape 20 cm from the end of the table. This is the
finish line.
3. Add 1,000 grams to your cart and record the total mass of (cart + 1,000 g) in the Data Table. Your
cart’s mass should be written on the cart. If not, your teacher will tell you the cart’s mass.
4. Hang a 50 g mass from a spring scale to measure its pulling force (in Newtons). Record this as your
first force on the data table.
Hanging heavy things from the spring scales will break the scales. Do not hang anything larger
than 500 g or 1 pound without first checking your scale’s tolerance with your teacher.
5. Holding the cart still, place the 50 g mass on the hanging end of the string.
6. In your data table, record the time it takes the cart to move the 40 cm between your two pieces of tape.
Complete a total of three trials.
 If you have an “outlier” (one datum that does not match the others), cross it out (do not
erase!) and do another trial so that your times for each pulling force are mostly consistent.
Safety! Have one person stop the cart before it rolls off the table.
7. Repeat for the following total masses hanging off the end of the string:
 100 grams total hanging mass
 200 grams total hanging mass
 300 grams total hanging mass
 400 grams total hanging mass
Yes
No
Warning: Multiple mass hanging. Hang smaller masses underneath larger ones
as the thin hooks on smaller masses break easily. No extended chains!
Complete three trials for each (more if data is inconsistent) and record forces and times in your
data table. Remember to stop the cart before it reaches the edge.
8. Gather all materials in your tub and check your lab kit back in to the teacher.
9. Tidy your lab station and complete the Calculations, Variables, and Conclusion/Analysis.
Variables:
in your journal
Manipulated (What are you changing in the lab?) –
Responding (What is responding to the manipulated variable?) –
Controlled (What stays the same? Find as many controlled variables as possible) -
Data:
Force vs Acceleration
Time (s)
Net Force
Distance
Cart Mass
on string
Traveled
(grams)
(N)
(cm)
Trial 1 Trial 2 Trial 3
Average
Time (s)
Average
Velocity
(cm/s)
Acceleration
(cm/s2)
2 * vavg
a
t
Conclusion and Analysis: in your journal
A. In general, as you increased the force on the cart, what happened to the cart’s acceleration?
B. Compare your data sets: as you double or triple the force on the cart, how does acceleration
change? (x2? x4? x ½? x 1/9?) Show with math, words or pictures what you think the
relationship is between force and acceleration. Justify your answer with data from the table.
C. What difficulties did you have in this lab, and how could improve the lab or your technique so that
they don’t happen again?
D. Give an example of how the relationship between force and acceleration might affect YOU.
(Examples: effort required to do something, limits on acceleration, how to control motion better…)
Newton's Second Law Lab (Part B: Mass)
Purpose:
To investigate the relationship between force, mass, and acceleration.
Background Information:
Newton's second law of motion deals with the acceleration of an object due to a net force. In this activity you
will use a cart to measure the acceleration as you change the mass of the cart. A falling mass will be used as a
force to pull the cart along the table. Finally you will graph each part's data and verify the relationships
presented in Newton's Second Law of Motion.
Investigative Question:
How will increasing the mass of a cart affect its acceleration?
Hypothesis:
in your journal
(If…then…because…)
Materials:
meter stick
~75 cm string
masking tape
cart
stopwatch
spring scale
500 gram and 1000 gram masses
pulley or metal rod
triple-beam balance
40 cm
60 cm
Warning: Hanging heavy masses off the end is dangerous! No Horseplay or unauthorized experiments.
Procedure:
The pulling force on the cart will remain the same. You will only increase the mass of the cart.
1. Set up your cart as shown in the picture above. Use tape to attach one end of the string to your cart.
2. Measure 60 cm from the end of the table and place a piece of tape there. This is where you the front end of
your cart will start. Place a second piece of tape 20 cm from the end of the table. This is the finish line.
3. Record the mass of your cart (written on the cart) as the first mass in your Data Table.
4. Add a 100 gram mass to the end of the string. Keep the same mass on the hanger for the entire experiment. Do
not add more mass to the hanger.
5. Record the pulling force (weight) of the 100 g mass in the data table. (If you do not remember this from
yesterday, hang the mass from a spring scale to measure its weight.)
One group member needs to be responsible for the cart staying on the table (rather than falling on the floor).
Make sure to catch the cart before it hits the pulley or bar.
6. In your data table, record the time it takes the cart to move the 40 cm between your two pieces of tape.
Complete a total of three trials. Repeat if your recorded times are not fairly consistent.
7. Repeat step # 6 with a 500 gram mass on top of the cart. Record the new total mass of the cart (calculate: cart
+ 500 grams = ______) and measured times in your Data Table.
8. Repeat for the following masses: cart + 1000 grams, cart + 1500 grams, cart + 2000 grams. Record
masses and times in your Data Table.
9. Return all materials and tidy your station. Complete the Calculations, Variables, and Conclusion/Analysis.
Variables:
in your journal
Manipulated (What are you changing in the lab?) –
Responding (What is responding to the manipulated variable?) –
Controlled (What stays the same? Find as many controlled variables as possible) -
Data: . . . You may write in this table to save lab time.
Time (s)
Net Force
Distance
Cart Mass
on string
Traveled
(grams)
(N)
(cm)
Trial 1 Trial 2 Trial 3
Conclusion and Analysis:
Average
Time (s)
Average
Velocity
(cm/s)
Acceleration
(cm/s2)
2 * vavg
a
t
in your journal
A. In general, as you increased the mass of the cart, what happened to the cart’s acceleration?
B. Compare your data sets: as you double or triple the cart mass, how much does acceleration change? (x2?
x4? x ½? x 1/9?) Show with math, words or pictures what you think the relationship is between force
and acceleration. Justify your answer with data from the table.
C. What is one controlled variable did you not consider or monitor well enough? What effect did it have, and
how might you reduce its effect?
Extension: in your journal
A. Give an example of how the relationship between mass and acceleration might affect YOU. ( Examples:
effort required to do something, limits on acceleration, how to control an object’s motion better…)
B. Combine your results from yesterday’s lab and today’s to come up with an equation linking force,
acceleration and mass.
C. Kari Ahn is pulling a bookcase across her bedroom floor. What are three reasons that she might find it hard
to accelerate the bookcase? (Hint: link to both labs as well as Newton’s 1st law.)