The point timer should be connected to an AC power supply.
It is necessary to measure the distance between two points on the paper tape with a scale.
Therefore: ad.
(2) According to the experimental principle and requirements: in the experiment, first turn on the power supply, then loosen the paper tape, then cut off the power supply, and finally remove the paper tape, so the order of the experimental steps is BADC. ..
(3) In order to reduce the experimental error, the lifted paper tape must be kept in a vertical position before being released, and its weight should be close to the dot timer. Therefore, the position of the resultant force is because of figure C.
(4)
A, because we are comparing the relationship between mgh and 12mv2, M can be compared without a balance, so A is wrong.
B, from h= 12gt2, it is found that the free-falling distance of the heavy hammer is H =12gt2 =12× 9.8× 0.022 ≈ 2mm in the first point cycle time t=0.02s, which shows that the resistance of the heavy object is very small and the experimental error is small, so B is.
C, D, In this experiment, the direct measurement includes: measuring the falling height of the heavy hammer with a scale. The acceleration of gravity has nothing to do with this experiment, but a predicted physical quantity. The instantaneous velocity of the weight corresponding to the falling height is calculated, so C and D are wrong.
E. Because there is resistance in this experiment, it is necessary to overcome the resistance during the falling of heavy objects, so the reduced gravitational potential energy is not completely converted into kinetic energy, so the experimental result must be that mgh is slightly larger than 12mv2, and 12mv2 cannot be slightly larger than MGH. Therefore, e is correct.
So: AE.
So the answer is: (1) ad; (2)BADC； (3)c； (4)AE。