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1、Experiment9Physics with Computers 9 - 1Newtons Second LawHow 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 carts velocity related to the force you apply? Or does the force just change the velocity? Also, wha
2、t 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 carts acceleration. The total mass of the c
3、art 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 Newtons second law of motion.Figure 1OBJECTIVESCollect force and acceleration data for a cart as it accelerates on a horizontal s
4、urface. Compare force vs. time and acceleration vs. time graphs. Analyze a graph of force vs. acceleration. Determine the relationship between force, mass, and acceleration.MATERIALSPower Macintosh or Windows PCLogger Pro LabPro or Universal Lab Interfacelow-friction dynamics cart Vernier Force Sens
5、or kg mass sets Vernier Motion DetectorExperiment 99 - 2Physics with Computers PRELIMINARY QUESTIONS (THINK ABOUT YOUR RESPONSES)1. When you push on an object, how does the magnitude of the force affect its motion? If you push harder, is the change in motion smaller or larger? Do you think this is a
6、 direct or inverse relationship?2. Assume that you have a bowling ball and a baseball, each suspended from a different rope. If you hit each of these balls with a full swing of a baseball bat, which ball will change its motion by the greater amount?3. In the absence of friction and other forces, if
7、you exert a force, F, on a mass, m, the mass will accelerate. If you exert the same force on a mass of 2m, would you expect the resulting acceleration to be twice as large or half as large? Is this a direct or inverse relationship?PROCEDURE1. Open the Logger Pro Program. The experiment file ( Newton
8、s 2nd Law) is located at N;CoursesRods PhysicsLogger pro Experments. 2. Connect a Dual-Range Force Sensor to Channel 1 on the LabPro Connect the Motion Probe to Dig/Sonic Channel 2The Logger Pro Program may not automatically detect the force probe. Click CONNECT and make sure the sensor name channel
9、 is correct.3.To get the best numerical results in the experiment, you will calibrate the force sensora. Choose Calibrate from the Experiment menu. b. Click the Force icon that appears in Channel 1. c. Click the button. d. Remove all weight from the Force Sensor and hold it vertically with the hook
10、pointed down. e. Type 0 in the Value 1 edit box. f. When the displayed voltage reading for Input 1 stabilizes, click Keep. 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 Keep.a
11、. When the displayed voltage reading for Input 2 stabilizes, click Keep, then click .Newtons Second LawPhysics with Computers 9 - 3You should check the calibration by measuring the weight of different masses. Find the mass of the cart with the Force Sensor. Record the mass in the data table. 4. Atta
12、ch 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 force sensor to its holder on the dynamics cart. Attach a string to the force Sensor and be sure it is long enough to connect to
13、 a slotted mass holder which should be hung over a pulley as shown in the figure. 6. Place the cart on a level surface. Make sure the cart is not moving and click , then click .Trials 7. You are now ready to collect force and motion data. Vary the FORCE acting on the cart (weight in the mass holder)
14、. Do not use too much force or the cart will move too quickly and the force calibration will not apply to your range. Protect the floor will a thin object ( an English or math text would do nicely-not your wonderful physics text)8. Note the shape of the force vs. time and velocity vs. time graphs. D
15、etermine the acceleration of the cart. Determine the avg force during the interval of the acceleration. Highlight section and press “STAT”. Record the Force and acceleration in the data table. 9. Repeat to determine average Force and acceleration. You should have 3 values of each to compute averages
16、.10. Use a different force (weight) and repeat. You should have at least 4 different forces11. Open Graphical Analysis. Make a graph of Force(y axis) vs Acceleration (x axis). Determine if a relationship can be determined.DATA TABLETrial I Data using cart Mass of Cart =_kgkgForceAcceleration Hanging weight (N)Trial 1 (N)Trial 2 (N)Trial 3 (N)Average Force (N)trial 1 (m/s2)trial 2 (m/s2)trial 3 (m/s2)Average a
