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**Unformatted text preview: **Newton’s Second Law
How does a cart change its motion when you push and pull on it? You might think that the harder
you push on a cart, the faster it goes. Is the cart’s velocity related to the force you apply? Or does
the force just change the velocity? Also, what does the mass of the cart have to do with how the
motion changes? We know that it takes a much harder push to get a heavy cart moving than a
lighter one.
A Force Sensor and an Accelerometer will let you measure the force on a cart simultaneously with
the cart’s acceleration. The total mass of the cart is easy to vary by adding masses. Using these
tools, you can determine how the net force on the cart, its mass, and its acceleration are related.
This relationship is Newton’s second law of motion.
A c c e le r o m e te r F o rc e S e n s o r Figure 1 OBJECTIVES Collect force and acceleration data for a cart as it is moved back and forth.
Compare force vs. time and acceleration vs. time graphs.
Analyze a graph of force vs. acceleration. Determine the relationship between force, mass, and acceleration. PROCEDURE
1. Open the file “09 Newtons Second Law” from the Physics with Computers folder.
2. Place the cart on a level surface. Make sure the cart is not moving and click
make sure both sensors are highlighted and click
. . Check to Trial I 3. Grasp the Force Sensor hook. Click
and take several seconds to move the cart back
and forth on the table. Vary the motion so that both small and large forces are applied. Make
sure that your hand is only touching the hook on the Force Sensor and not the Force
Sensor or cart body.
4. The graph of force vs. acceleration should appear to be a straight line. To fit a straight line to
the data, click on the graph, then click the Linear Fit button, . Record the equation for the
regression line in the data table. 5. Using the graphs, estimate the acceleration of the cart when a force of 1.0 N has acted upon
it. Select Interpolate from the Analyze menu. Move the mouse across the graph and determine
the acceleration (x) when the force (y) is nearly 1.0 N. Record the force and acceleration in
the data table.
6. Repeat Step 5 using a force of –1.0 N.
7. Draw each graph.
Trial 2 8. Attach the additional mass to the cart. Record the mass of the cart, sensors, and additional
mass in the data table.
9. Repeat Steps 3 – 7. DATA TABLE
Trial I
Mass of cart with sensors (kg)
Regression line for force vs. acceleration data Force pulling cart (N) 2 Acceleration (m/s ) Force closest to 1.0 N
Force closest to –1.0 N Trial 2
Mass of cart with sensors and additional mass (kg)
Regression line for force vs. acceleration data Force pulling cart (N)
Force closest to 1.0 N
Force closest to –1.0 N 2 Acceleration (m/s ) ANALYSIS
1. Compare the graphs of force vs. time and acceleration vs. time for a particular trial. How are
they different? How are they the same?
2. Are the net force on an object and the acceleration of the object directly proportional?
Explain.
3. What are the units of the slope of the force vs. acceleration graph? Simplify the units of the
slope to fundamental units (m, kg, s).
4. For each trial compare the slope of the regression line to the mass being accelerated. What
does the slope represent?
5. Write a general equation that relates all three variables: force, mass, and acceleration. ...

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- Spring '08
- Kenney
- Chemistry, Force, Mass