(20 1 1? When verifying the law of conservation of mechanical energy by falling body method, a classmate chose the paper tape as shown in the figure according to the correct operation, where O is the

(20 1 1? When verifying the law of conservation of mechanical energy by falling body method, a classmate chose the paper tape as shown in the figure according to the correct operation, where O is the starting point. The (1) mm scale is used to measure the length, and the next bit of the smallest scale needs to be read.

Of the three data, OC segment: 15.7, which does not meet the requirements of effective digital reading, should be recorded as 15.70cm. ..

(2) the decrease of gravitational potential energy △ EP = mgh = 9.8× 0. 1.242m? J = 1.22 MJ

The instantaneous speed at the middle moment is equal to the average speed in the process of finding the speed of b:

VB = SAC0.02× 2 =1.55m/s

EkB= 12mv2B= 1.20mJ

Because there is frictional resistance in the falling process, the increase of kinetic energy is less than the decrease of potential energy.

Therefore, fill in: greater than; Because friction generates heat, part of the reduced gravitational potential energy is converted into internal energy.

(3)EkB = 12mv2B = 12m(9.8×0.02×8)2 = 1.23 mj

That is, the decrease of gravitational potential energy is less than the increase of kinetic energy, because V is calculated according to free fall, and the actual motion is not free fall, so there is resistance, and the corresponding falling height is greater than the measured height.

So the answer is: (1) oc; 15.70cm

(2) 1.22m； 1.20m； Greater than; Because friction generates heat, part of the reduced gravitational potential energy is converted into internal energy.

(3)1.23m; Less than; V calculated by free fall, the corresponding falling height is greater than the measured height.