3.1.4 Experimental procedures
1)Flatten the air track
Turn on the gas supply device and place a sliding block on air track,and then the leveling state can be judged according to the state of the sliding block.
(1)Judging in the stationary state:when the air track is leveling,the sliding block can be stabilized at any position on the track.
(2)Judging in the state of motion:when the sliding block moves on the air track,the velocity remains unchanged or the acceleration is zero.
2)Incomplete elastic collision experiment
(1)Preparation:The photoelectric gates are fixed at A and B positions about 40 cm apart.The function of the computer counter is set to measure the speed,and the unit is also converted to the speed unit accordingly.Check the states of the light baffle and spring of the sliding block to ensure that the light baffle is valid and the head-on collision occurs when the sliding block passes through the photoelectric gate.(https://www.daowen.com)
(2)Select the collision location:Place the sliding block 1 and 2 between doors A and B,as is shown in Figure 3.1.2(the springs of the two sliding blocks just touch each other,and the small sliding block is on the side of door B),and then record the central positions of the two sliding blocks,namely positions C and D.
(3)Measure v1A,v2B and v1B:Place the small sliding block 2 in position D and make it motionless(v20=0),gently push the large sliding block 1 to the back spring equipped in the rear end of the track,which can bounce the sliding block 1 back to collide the sliding block 2,and then record the corresponding velocities before and after the collision.
(4)Velocity correction:Referring to Figure 3.1.2,the values of a10,a1 and a2 can be measured respectively.When we measure the acceleration,the velocity of the sliding block should be almost equal to that at the time of collision.Especially,in order to reduce the measurement error,the measurement should be repeated about 3～5 times to get the average value.
3)Complete inelastic collision experiment
The collision surfaces of the two sliding blocks should be placed with nylon tape for collision and the spring is removed,and make sure v20=0.Then the experimental observation and data recording methods are similar to that in content 2).
