Question
Please help me with my lab questions. The expt is provided. This is also my last question so please answer only if you're fully confident and are willing to answer all of them. thank you.
PROCEDURE A: Acceleration Due to Gravity 1. Adjust the power supply to 1.5 V 2. Close the switch to energize the electromagnet 3. Place the body that is too full at the bottom of the electromagnet so that it will attach itself to the magnet. Steady it from swaying by momentarily touching it with your hand Set the spark timer for 60 Sparks per second and record this value on your data sheet as 60 Sparks per second. Take the reciprocal of the sparks per second to give you the time between sparks, called the spark timer Delta. Hence, the spark timer interval is 160 second. Have another student are in the spark timer power switch to on Turn the spark timer spark switch to on. Sparks will be observed to move from the outer wire across the ring on the body and through the tape to the inner wire, leaving marks on the tape at the points where the sparks crossed. 4. 5. 6 Open the switch to the electromagnet. This will cause the body to fall. As the body descends, Sparks 7. As soon as the body reaches the bottom, turn the spark timer spark switch to off and the power switch to 8. Pull the sensitized paper over the top of the free-fall apparatus until you have all the paper with the dots will enter the paper every 1/60 s, leaving a trace of the location of the body as a function of time off on it. Tear this piece off and attach the clip to the rest of the paper so that the apparatus will be ready for the next group Lay the waxed paper on the desk and observe the dots. Start at the first dot called the zeroth dot, circle it, and label it y-0 and t-0. You should use every second as a data point Record the number of time intervals between circled dots on your data sheet. 9. 10. Measure the distance from the zero stop to the first circle. Call this distance yi. The distance from the zeroth dot to the first circled dot is measured as ys Now measure the distance from the zeroth dot to each successive circle as ys, ys, ys etc, and record these numbers in meters on your data sheet in the column Total distance fallen y"
Explanation / Answer
1. No, it does not matter because the calculation of g from the experiments involves change velocity which
comes from the change in position measured and also change in time measured by the spark timer.
2. Note that velocity in this experiment depends linearly on time. Therefore, average velocity within a time interval is equal to the velocity at the middle of interval. For this reason, the velocity should be plotted at the middle of interval.
3. The spark timer interval should not exceed a certain value so it does not leave any mark on the waxed paper. On the other hand, keeping it too small will give very closely spaced dots or unnecessary a large number of data points.
4. If the falling body oscillates then dots on the waxed paper may not be lying on a straight line which will
introduce error in the measurement.
6. It would instantly appear that the simplest way to measure the reaction time is to use a stop watch. However our reaction time itself would prevent an accurate measurement our reaction time. Therefore an indirect measurement (often used) such as using the distance traveled by falling meter stick is used.