Steps of measuring gravity acceleration by air cushion guide rail

I. Horizontal adjustment of air cushion guide rail

Adjusting the level of the guide rail is the key to do the experiment well. If the guide rail is equipped with a level gauge, the nut can be adjusted to observe the display state of the level gauge. When the guide rail is horizontal, the resultant force of the slider in the horizontal direction is zero. At this time, the slider is stationary or moves in a straight line at a constant speed. However, it is difficult for the slider to be completely stationary, because the machining of the air rail cannot be absolutely straight. If you push the slider slightly, the slider will move from one end to the other, and the sum of the time through the two photogates should be equal. Due to air resistance, the speed of the slider will slowly decrease. The time after passing the last photogate is always longer than that after passing the previous photogate. After careful adjustment, the time difference between the two photoelectric doors does not exceed 65438 0%, at least when moving to the pulley. At this point, the guide rail can be considered as leveled.

Second, the measurement of acceleration.

Start the air source to supply air to the air rail, and wipe the surface of the guide rail and the inner surface of the slider with clean cotton yarn dipped in alcohol.

1. Put two identical photoelectric doors at different positions of the guide rail and connect them with the digital millisecond meter as required. Turn on the power supply of the millisecond meter, the light beam emitted by the spotlight bulb shines on the slit of the photosensitive tube, turn on the air source, and make the slider with the hood move freely on the guide rail. Adjust a screw on the guide rail to make the slider move back and forth slowly in a small range (not always in one direction) on the guide rail, and then the guide rail is basically horizontal. Push the slider gently to get a certain speed. When the slider moves from one end to the other, it passes through two photogates in turn (the order is reversed when it returns), and the sum of the time when the slider passes through the two photogates is read from the millisecond meter.

2. Turn the timing mode switch of the digital millisecond meter to position A, put a pad with thickness H under the anchor screw at one end of the troublemaker, put the slider at the highest point of the guide rail to let it slide freely, and record the time interval t 1 and t2 when the slider passes through the two photoelectric gates. Repeat the above five times and record the data (the measurement of acceleration requires the initial conditions to remain unchanged).

3. Measure the width of the light blocking plate with vernier caliper and record it;

4, measure that distance s between the two photoelectric gates and record;

5. Turn off the millisecond meter, remove the slider, turn off the air pump, and arrange and restore together.

Precautions:

The air rail is a high-precision experimental device, and the surface of the guide rail and the inner surface of the slider have high smoothness and good cooperation. Therefore, each group of guide rails and sliders can only be used together and cannot be interchanged with other groups. In the experiment, it is necessary to prevent knocking and scratching the guide rail and slider (especially the slider can not fall to the ground). Don't slide the slider on the guide rail when there is no ventilation to avoid scratching the surface; After use, remove the slider first, and then turn off the air supply; When there is dirt or dust on the surface of guide rail and slider, cotton yarn can be wiped clean with alcohol; The air holes on the surface of the guide rail are small and easy to block, which affects the movement of the slider. Please check carefully after introducing compressed air. If the air hole is blocked, you can gently poke it with a thin steel wire smaller than the diameter of the air hole. After the experiment, the rail surface should be wiped clean and covered with dust cover.