3.1.2 Experimental instruments
Air track,sliding block,photoelectric door,general computer counter,nylon sticky tape,etc.
Figure 3.1.1 Air track
1—Surface of track;2—Track;3—Supporting feet;4—Sliding block;5—Pulley;6—Air inlet
1)Air track
Air track(Figure 3.1.1)is a new mechanical experimental instrument invented in the 20th century.It is mainly composed of a 1.5 meter-long hollow track and the sliding block.There are several air holes on the smooth surface of the air track.The supporting feet installed under the track are used to adjust the level of the air track.The photoelectric gate is installed on the track to detect the corresponding time.
(1)Surface of the track:The air track is made of aluminum alloy,about 1 500 mm or 1 800 mm long,and 50 mm wide.There is a 90° included angle between the two smooth planes.Moreover,each side has two rows of 0.5 mm air holes with about 20 mm hole center distance.
(2)Track:A hollow structure made of aluminum alloy.
(3)Supporting feet:Three-point structure and adjustable screws,where one foot at one end and two feet at the other end.
(4)Sliding block:It is made of aluminum alloy and possesses a smooth inner surface,which is consistent with the rail surface.The light baffle and the spring can be respectively placed above the slide top and its two ends.
(5)Pulley:Composed of the plastic pulley and the clock pendulum needle,the pulley weighs 0.3 g can flexibly rotate.(https://www.daowen.com)
(6)Air inlet:It is used to collect the external gas supply device.
2)Application methods and attentions
We should firstly connect the air supply,vent pipe and track,then turn on the air supply device to assure about 1 standard atmosphere gas ejection from air holes of track.In the following,the sliding block can be placed on the track and some researches can be conducted.The sliding block can be approximately used as an ideal movement body with little sliding friction,therefore,the experimental results can be almost identical to that without sliding friction.During the experiment,some attention points are in the following:
(1)Do not vibrate or weigh the air track to avoid deformation.
(2)Avoid collisions between the rail surface and the sliding block.Handle the sliding block with care to prevent falling,which may lead to damage or deformation.
(3)The rail surface and the inside surface of the sliding block should be kept dry and clean,and they should be cleaned regularly with anhydrous alcohol.
(4)During the experiment,we must first turn on the air supply device,and then put the sliding block gently on the rail surface.After finishing the experiment,we must first remove the sliding block,and then turn off the air supply device.Do not place or move the sliding block on the rail surface when no air is supplied!
(5)The compressed air into the track must be dried and filtered.Water vapor,oil and impurities should be strictly prohibited to avoid blocking of air holes or damaging the air track.
(6)When the experiment is over,the air track should be covered with the tablecloth to prevent dust.
(7)If the air holes are blocked,we should clean the air holes with 0.5～0.8 mm steel wire,and clean them with anhydrous alcohol.
