Download AAAAA

Team Names: __________________________ Period: ______ Date: ________________
Inquiry Lab Instruction—Newton’s Second Law (Updated 25 Oct 16)
In this lab students will investigate how the acceleration of an object is related to its mass and the
force exerted on the object, and use experimental results to derive the mathematical form of
Newton’s second law.
This is a guided inquiry where you will answer the question, “What factors affect the
acceleration of a system?”
You are welcome to use anything in the lab environment to accomplish this lab but the basics
include a dynamics track, green cart, slotted masses, the mass hanger for the slotted masses,
pulley (mounts to table’s edge), string, meter stick, stopwatch, video recorder (phone).
Here is one recommended setup:
In the end you will need a data table with the acceleration for each situation, the mass of the cart,
the mass of the system and the mass of the force applied. You will need this data to plot
Acceleration vs. Force, Acceleration vs. Mass and Acceleration vs. 1/Mass graphs. It is most
accurate to use video analysis to determine the actual acceleration of the system.
Keep careful notes on each phase of this lab so you can replicate
your assigned section on the white board.
Prelab Part I.. Cart with no additional weight, constant weight for the force applied.
Predict what the graph of the cart’s velocity (v) versus time (t) will look like after the system is
released from rest. Provide a drawing of your prediction on your whiteboard.
[Draw your predictions here or in your notebook.]
Conduct the experiment several times and graph the results. You will need some method to
determine acceleration, video analysis is most accurate.
Compare the prediction to actual findings.
[Diagram your findings and compare them to your predictions here or in your notebook.]
If you do both, compare the video analysis to the manually timed graph.
Prelab Part II. In this scenario you will leave the force applied constant (hanging weight) and
increase the carts mass. Collect data on at least four runs.
First, calculate a theoretical value for the carts acceleration given each applied force. Try to
figure out the equation yourself. Ask if you need help with it.
a) Predict what the graphs will look like if the cart’s mass is increased. Will the new velocity
versus time graph look the same or different from the graph in Part I? Draw your prediction.
Conduct the experiment several times and graph the results.
Compare the prediction to actual findings.
If you do both, compare the video analysis to the manually timed graph.
b) Predict what the graphs will look like if the hanging mass is increased. If the hanging mass is
increased, will the new velocity versus time graph look the same or different from the graph in
Part I? Draw your prediction.
Investigation Part I. As a group, demonstrate what happens to the systems acceleration when
the total mass of the system is constant but the net force is varied. How can the mass stay the
same but the net force vary? [HINT: Move weights from the cart to the string to alter the
acceleration but keep the system mass the same.]
What do you observe?
What can you measure?
What can you change?
Investigation Part II.
Now, design two data collection strategies to determine how two factors affect the acceleration
of the system: the net force on the system and the total mass of the system.
Activity 1. Design procedures that include calculations of the acceleration when the total mass
of the system is kept constant and the net force is varied.
Activity 2. Design procedures that include calculation of the acceleration when the total mass of
the system is varied and the net force is kept constant.
Analysis.
Discuss how your data indicated if the acceleration was proportional to force.
What does the slope of the acceleration versus force graph represent?
What is the algebraic relationship between acceleration and net force in this system?
How does the data indicate if the acceleration was inversely proportional to the mass?
What does the slope of the acceleration versus the invers of mass represent?
What is the algebraic relationship between acceleration and mass in this system?