Motion Measurement

运动测量

Write down your expectations.

写下你的预期

Make a guess about how fast you can turn a stopwatch on and off. 1 second? 10 seconds? 0.1 seconds? 0.01 seconds?

你猜一下自己能多快地启动和关闭一个秒表？1秒？10秒？0.1秒？0.01秒？

If you just sit the wooden channel up on the wooden block and roll the ball down it, what is you guess about how long it will take to roll down the incline?

Suppose you measured the time for the ball to roll down the ramp from a given height. If you raise the ramp to twice as high, will it cut the time in half? more than half the time? less than half the time?

假设你测量了球从给定高度沿斜坡滚下的时间。如果将斜坡抬高到两倍的高度，时间会减半吗？会超过一半的时间吗？会少于一半的时间吗？

如果你只是把木制通道放在木块上，然后让球从它上面滚下，你猜它需要多长时间才能滚下斜面？

Physical measurements are never exact, and it is important to assess the uncertainty in measurements. One way to do this is to repeat measurements and average the results. The maximum deviation from the average is one way to assess uncertainty (although not the best way). In the following measurements, measure each case at least three times and take an average. Then record the number like the following example.

物理测量从不绝对精确，评估测量中的不确定性非常重要。一种方法是重复测量并取平均值。最大偏差可以用来评估不确定性（尽管不是最佳方法）。在以下测量中，每个情况至少测量三次并取平均值。然后按照以下示例记录数值。

Measured times:
测量时间：
5.6 sec
6.0 sec
6.2 sec
Sum 17.8 sec ÷ 3 = 5.9 sec average
5.6 秒 6.0 秒 6.2 秒总和 17.8 秒 ÷ 3 = 5.9 秒平均值

Experimental time: 5.9 ± 0.3 sec since the maximum deviation from the average is 0.3 sec.

(Checking one-by-one: 5.9-5.6 = 0.3, 5.9-6.0 = -.1, 5.9-6.2 = -.3, so the biggest difference has a size 0.3 . Using this maximum deviation from your average as your estimate of measurement uncertainty gives you a sort of "worst case" estimate of the uncertainty of your measurement.)

实验时间：从最大偏差0.3秒开始算起，为5.9±0.3秒。（逐一检查：5.9-5.6=0.3，5.9-6.0=-0.1，5.9-6.2=-0.3，所以最大偏差为0.3。用这个最大偏差作为测量不确定性的估计，可以得到一种‘最坏情况’下的测量不确定性的估计。）

1. Start and stop the stopwatch as quickly as you can. This will give you a measure of your reaction time.

开始和停止秒表要尽可能快。这将给你一个反应时间的测量。

Reaction time
反应时间
__________
__________
__________

Experimental reaction time ___________ ± ___________ sec.

实验反应时间 ___________ ± ___________ 秒。

2. Drop the ball provided from a height of one meter and measure the time required to hit the floor. Find an experimental fall time by the above procedure.

2. 将一个从1米高处释放的球滴落，测量其击中地面所需的时间。通过上述步骤获取实验测得的下落时间。

3. Assemble the track so that the bottom of the ball in its starting position may be positioned 2 cm above the flat surface (basically, this will mean just sitting the end of the track on top of the supporting block). Let the ball roll down the incline and measure the time when it leaves the track at the bottom end. Measure the length of the track so that you may calculate the average speed.

3. 将轨道组装好，使球在起始位置时底部位于平坦表面以上2厘米处（基本上，这意味着只需将轨道末端放在支撑块上）。让球沿斜面滚动，并测量它离开轨道底部端时的时间。测量轨道的长度，以便计算平均速度。

4. Will doubling the height of the upper end of the incline cut the time in half? Measure it and find out.

将斜面顶端的高度加倍，是否能将时间减半？进行测量以验证。

5. What height will cut the roll time in half? Experiment and find out. Record the height and the times for your closest approach to half the time in part 3.

5. 哪个高度会使滚落时间减半？进行实验找出答案。记录你接近第三部分一半时间时的高度和时间。

6. Referring to your data in part 3:
What uncertainty in time measurement would you expect to come from your starting and stopping the stopwatch? (Hint: see part 1). __________

参考你第三部分的数据：你预计从启动和停止秒表时会引入多大的时间测量不确定性？（提示：见第一部分）。__________

What is the average velocity for part 3? __________

第3部分的平均速度是多少？__________

What is the velocity of the ball at the bottom of the track in part 3? ___________

Equipment: Motion Measurement

设备：运动测量

Wooden channel made of corner molding
由角饰制成的木制通道
3 x 3 inch wooden blocks, drilled for dowel rod
3英寸×3英寸的木块，带有木钉孔
1/4" dowel rod
1/4英寸木栓杆
metal clip for use in adjusting height
用于调节高度的金属夹子
stopwatch
秒表
meter stick
米尺

第3部分中球在轨道底部的速度是多少？

Index

Hands-on Exercise List

索引实验操作列表

HyperPhysics***** NSCI 3001

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