Physics Lab Report for Motion

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the curve and X axis. Let positive X axis to be positive direction, this object initially go along X negative side for it moves positive 0.32m before changing direction.

Similarly, it moves negative 0.2m before again changing direction.

To sum up,

So the greatest displacement is |-0.32+0.2-0.26|=0.38m at the 8th s

4. |-0.32+0.2-0.26+0.2|=0.18m, so it was 0.18m from the starting point (negative side)

Part 3, detect motion of a glider on an inclined air track.First, we measured required data, calculated theoretical acceleration

Then, we conducted experiment and selected three best run as follows.

What we got from Capstone’s calculation of acceleration stayed far from ideal graph’s. Its magnitude jumped between -0.4 to 0.8 (compare to a=0.57), which indicated that each part of the air track’s friction might differ greatly, the air drag should not be ignored in real operations, the systematic error could be greater than the data showed in instruction, etc.

Discussion

For part1&3, which required motion sensor and Capstone, we found the digit display on position-time graphs fluctuates sharply. As for first range of experiment, whose maximum position ,was 0.7m, the fluctuation could reach 7.0m at its peak. These circumstances usually happened by the end of one run. We made reasonable assumption that the sound wave wasn’t reflect when it hit the note book, instead, it hit the wall around 7 meters away. To help the motion sensor perform satisfactorily, following steps were tried:

improved the target by replacing the notebook with blocker to better reflect ultrasound;

removed any interfering object near target or sensor (operator: leaned back with hand holding the blocker from the back) ;

adjusted sample rate until it achieve its smoothest curve;

aimed the sensor slightly up to avoid detecting air track;

set the range switch to from short range to long.

Q5.5.1.Sound waves are considered to be longitudinal waves, which means that particles in the air surrounding (called medium) move in parallel motion to the waves. Naturally, the density and temperature change the medium’s physical property and further affect sound speed. The gas flux is by no mean homogenous and changeable, so the sound speed varies everywhere.

Q5.5.3.the unit of sample rate is Herz, which represents the number of emit per second. In this case, we use theoretical average sound speed 344m/s for calculation. Plus, sound covers twice of the length.

Q5.5.4. in this case, we can only give the uncertainty of systematical margin of error:%

Q5.5.6. error in measurements: reading error (uncertainty ); timing uncertainty ()

Error in capstone: systematic error% ; sound speed difference (unpredictable)