Newton’s Second Law Lab
Objective:
We will study the effects of a constant force on carts with varying mass. Through
analysis of the acceleration of the cart, we can verify the equation, Fnet = ma, Newton’s
second law.
Materials:
Motion Sensor and DataStudio
ramp, cart, pulley, string, triple beam balance
wooden board, mass hanger, assorted masses
Procedure:
1. Set up the equipment as directed by the instructor. The ramp should be flat, not inclined.
2. Use a triple beam balance to determine the mass of the cart. Record it on the back of this
page.
3. Attach 50 g to the mass hanger. This hanging mass does not change and will be used for
the whole experiment. Measure the hanging mass using the triple beam balance, convert
g to kg, and record.
4. Calculate the weight of the hanging mass in newtons. This is the amount of force the
hanging mass will produce. Record.
5. To compensate for friction in our setup we need to remove 40% from our force.
Use the formula:
Fnet = 0.6 x force of hanging mass
Record the Fnet.
6. Load the cart with 500 g. Record the Mass of Cart & Load for Trial 1.
7. Calculate and record the Theoretical Acceleration. Use the formula:
theoretical acceleration =
_____Fnet______
mass of cart & load
8. Attach the cart to the hanging mass. Use the motion sensor to determine the acceleration
of the cart (use the velocity vs. time graph). Record the Measured Acceleration. Repeat
this run and take the average.
9. Calculate and record the percent error. Use the formula:
percent error =  measured acceleration – theoretical acceleration  x 100
theoretical acceleration
10. Repeat for a total of five trials, each time reducing the mass in the cart by 100 g.
Data Tables
Mass of cart:_______________ kg
Hanging mass:_____________ kg
Trial
Force of hanging mass:____________ N
Fnet = __________________________ N
Mass of
Theoretical
Cart &
Acceleration Measured Acceleration (m/s2)
Load (kg) (m/s2)
Run 1
Run 2
Ave.
Percent
Error
(%)
*Inverse of
Mass of
Cart &
Load (kg)
1
2
3
4
5
Average Percent Error. Add the absolute values of the five
trials, and then divide by five.
* “Inverse of Mass” is one divided by the mass of the cart plus load.
Graph:
In Excel, create a scatter point graph “Measured Acceleration vs. Inverse of Mass” (remember, y
vs. x). Include all the important elements of a graph. Print your graph and include it with your lab
report.
Questions:
1. Refer to your graph. What is the slope of the line of best fit?
2. What physical quantity does this slope represent?
Analysis and Conclusion:
For your lab report, be sure to:
- compare your measured and theoretical accelerations
- discuss sources of error that may account for any differences
- answer the question, “Does my data support the equation F = ma?”. Give evidence.