It is known that the initial velocity is zero and the displacement is L. To calculate the acceleration, we need to know the final velocity, so we need to use a digital timer to read the time t when the shutter bar passes through the photoelectric gate B.
Then we can know that the speed of the slider reaching the photoelectric gate is v=dt, and then according to the relationship between the speed and displacement of uniform acceleration, we can get: a = v2? 02L=d22Lt2
Therefore, the digital timer reads the time t when the shading bar passes through the photoelectric gate B.
(2)A, the tension is directly measured by the sensor, so it has nothing to do with the relationship between the car quality and the hook code quality, so A is correct.
B, the distance from position A to the photoelectric gate is larger, which is beneficial to reduce the error, so B is wrong.
C, air cushion guide rail should be adjusted horizontally, so that the pulling force is equal to the resultant force, so C is wrong.
D, keep the direction of the cable parallel to the air cushion guide rail, and the pulling force is equal to the resultant force, so D is wrong.
So choose: a.
(3) According to Newton's second law, F = horse and A = V2? 02L=d22Lt2, so f = md22lt2.
So the answer is: (1) vernier caliper; Time t; (2) A; (3)Md22Lt2。