什么物理实验,目的,原理Static and Kinetic FrictionIf you try to slide a heavy box resting on the floor,you may find it difficult to get the box moving.Static friction is the force that is acting against the box.If you apply a light horizonta

什么物理实验,目的,原理Static and Kinetic FrictionIf you try to slide a heavy box resting on the floor,you may find it difficult to get the box moving.Static friction is the force that is acting against the box.If you apply a light horizonta
什么物理实验,目的,原理
Static and Kinetic Friction
If you try to slide a heavy box resting on the floor,you may find it difficult to get the box moving.Static friction is the force that is acting against the box.If you apply a light horizontal push that does not move the box,the static friction force is also small and directly opposite to your push.If you push harder,the friction force increases to match the magnitude of your push.There is a limit to the magnitude of static friction,so eventually you may be able to apply a force larger than the maximum static force,and the box will move.The maximum static friction force is sometimes referred to as starting friction.We model static friction,F­­static,with the inequality Fstatic m­s N where m­s is the coefficient of static friction and N the normal force exerted by a surface on the object.The normal force is defined as the perpendicular component of the force exerted by the surface.In this case,the normal force is equal to the weight of the object.

什么物理实验,目的,原理Static and Kinetic FrictionIf you try to slide a heavy box resting on the floor,you may find it difficult to get the box moving.Static friction is the force that is acting against the box.If you apply a light horizonta
这个就是静摩擦与动摩擦.主要先说的是,如果你推一个很沉的箱子,你会发现你很难让箱子移动.静摩擦就是使箱子静止的力.如果你轻轻推箱子,静摩擦力就很小,用力推箱子,静摩擦力就很大.当然,这是有一个界限的的.当你作用在箱子上的力大于最大静摩擦力,那么箱子就被你推动了.
然后就是在解释公式……F=μN 求动摩擦.N是支持力,F是摩擦力,μ是摩擦系数.剩下的你就自己百度去吧……

Procedure
Part I Starting Friction
1. Measure the mass of the block and record it in the data table.
2. Connect the Force Sensor to Channel 1 (Student Force Sensor and Dual-Range For...

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Procedure
Part I Starting Friction
1. Measure the mass of the block and record it in the data table.
2. Connect the Force Sensor to Channel 1 (Student Force Sensor and Dual-Range Force Sensor) of the LabPro or Universal Lab Interface or to the PORT 1 input (ULI Force Probe) of the Universal Lab Interface.
3. Open the Experiment 12 file from Physics with Vernier. Then open the experiment file that matches the force sensor you are using. Set the range switch on the Force Sensor to 50 N. One graph will appear on the screen. The vertical axis will have force scaled from 0 to 20 Newtons. The horizontal has time scaled from 0 to 5 seconds.
4. Tie one end of a string to the hook on the Force Sensor and the other end to the hook on the wooden block. Place a total of 1 kg mass on top of the block, fastened so the masses cannot shift. Practice pulling the block and masses with the Force Sensor using this straight-line motion: Slowly and gently pull horizontally with a small force. Very gradually, taking one full second, increase the force until the block starts to slide, and then keep the block moving at a constant speed for another second.
5. Hold the Force Sensor in position, ready to pull the block, but with no tension in the string. Click Zero at the top of the graph to set the Force Sensor to zero.
6. Click to begin collecting data. Pull the block as before, taking care to increase the force gradually. Repeat the process as needed until you have a graph that reflects the desired motion, including pulling the block at constant speed once it begins moving. Print or copy the graph for later reference. Choose Store Latest Run from the Data Menu to store the run as Run 1 for later analysis.
Part II Peak Static Friction and Kinetic Friction
In this section, you will measure the peak static friction force and the kinetic friction force as a function of the normal force on the block. In each run, you will pull the block as before, but by changing the masses on the block, you will vary the normal force on the block.
Figure 1
7. Remove all masses from the block.
8. Click to begin collecting data and pull as before to gather force vs. time data.
9. Examine the data by clicking the Statistics button, . The maximum value of the force occurs when the block started to slide. Read this value of the maximum force of static friction from the floating box and record the number in your data table.
10. Drag across the region of the graph corresponding to the block moving at constant velocity. Click on the Statistics button again and read the average (or mean) force during the time interval. This force is the magnitude of the kinetic frictional force.
11. Repeat Steps 9-11 for two more measurements and average the results to determine the reliability of your measurements. Record the values in the data table.
12. Add masses totaling 250 g to the block. Repeat Steps 9 – 12, recording values in the data table.
13. Repeat for additional masses of 500, 750, and 1000 g. Record values in your data table.
Part III Kinetic Friction Again
In this section, you will measure the coefficient of kinetic friction a second way and compare it to the measurement in Part II. Using the Motion Detector, you can measure the acceleration of the block as it slides to a stop. This acceleration can be determined from the velocity vs. time graph. While sliding, the only force acting on the block in the horizontal direction is that of friction. From the mass of the block and its acceleration, you can find the frictional force and finally, the coefficient of kinetic friction.

Figure 2
14. Connect the Motion Detector to DIG/SONIC 2 of the LabPro or PORT 2 of the Universal Lab Interface. Open the experiment file Exp 12 Motion Detector. Two graphs will appear on the screen. The vertical axis of the top graph will have distance scaled from 0 to 3 m, and the lower graph has velocity scaled from ­– 2 to 2 m/s. The horizontal has time scaled from 0 to 5 s.
15. Place the Motion Detector on the lab table 2 – 3 m from a block of wood, as shown in Figure 2. Position the Motion Detector so that it will detect the motion of the block as it slides toward the detector.
16. Practice sliding the block toward the Motion Detector so that the block leaves your hand and slides to a stop. Minimize the rotation of the block. After it leaves your hand, the block should slide about 1 m before it stops and it must not come any closer to the Motion Detector than 0.4 m.
17. Click to start collecting data and give the block a push so that it slides toward the Motion Detector. The velocity graph should have a portion with a linearly decreasing section corresponding to the freely sliding motion of the block. Repeat if needed.
18. Select a region of the velocity vs. time graph that shows the decreasing speed of the block. Choose the linear section. The slope of this section of the velocity graph is the acceleration. Drag the mouse over this section and determine the slope by clicking the Linear Regression button, . Record this value of acceleration in your data table.
19. Repeat Steps 18 – 19 four more times.
20. Place masses totaling 500 g on the block. Fasten the masses so they will not move. Repeat Steps 18 – 19 five times for the block with masses. Record acceleration values in your data table.
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