Newtons Second Law Experiment

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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.

[pic]

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.

Materials

|POWER MACINTOSH OR WINDOWS PC |LOGGER PRO | |LABPRO OR UNIVERSAL LAB INTERFACE |LOW-FRICTION DYNAMICS CART | |VERNIER FORCE SENSOR |0.500 KG MASS | |VERNIER LOW-G ACCELEROMETER | |

Procedure

1. OPEN THE EXPERIMENT (09 – DOUBLE CHECK THE TITLE) FILE FROM PHYSICS WITH VERNIER. THREE GRAPHS WILL APPEAR ON THE SCREEN, AS SHOWN IN FIGURE 2.

[pic]

Figure 2

2.Connect a Student Force Sensor or Dual-Range Force Sensor to Channel 1 on the LabPro or Universal Lab Interface. (If you are using a Force Probe, connect the probe to PORT 1.) Connect the Low-g Accelerometer to Channel 2 on the interface.

3.To get the best numerical results in the experiment, you will calibrate both sensors.

a. Choose Calibrate from the Experiment menu.
b. Click the Force icon that appears in Channel 1. (If you are using the ULI Force Probe, click the icon in PORT 1.) c. Click the [pic] button.
d. Remove all weight from the Force Sensor and hold it vertically with the hook pointed down. e. Type 0 in the Value 1 edit box.
f. When the displayed voltage reading for Input 1 stabilizes, click [pic]. g. Add the 0.500 kg (4.9-N) mass to the hook of the Force Sensor. h. Type 4.9 in the Value 2 edit box.
i. When the displayed voltage reading for Input 1 stabilizes, click [pic].

4.Click the Acceleration icon that appears in Channel 2.

a. Click the [pic] button.
b. Point the arrow on the Accelerometer straight down. (It is important that the sensor is vertical and held steady. You may want to hold the sensor against a table top to steady it.) c. Type – 9.8 in the Value 1 edit box.

d. When the displayed voltage reading for Input 2 stabilizes, click [pic]. e. Point the Accelerometer arrow straight up.
f. Type 9.8 in the Value 2 edit box.
g. When the displayed voltage reading for Input 2 stabilizes, click [pic], then click [pic]. 5.Attach the Force Sensor to a dynamics cart so you can apply a horizontal force to the hook, directed along the sensitive axis of your particular Force Sensor. Next, attach the Accelerometer so the arrow is horizontal and parallel to the direction that the cart will roll. Orient the arrow so that if you pull on the Force Sensor the cart will move in the direction of the arrow. Find the mass of the cart with the Force Sensor and Accelerometer attached. Record the mass in the data table.

6.Place the cart on a level surface. Make sure the cart is not moving and click [pic], then click [pic].

Trial I

7. You are now...
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