In order to explore "which of the wooden blocks and iron blocks with the same bottom area has a rougher lower surface", Xiao Di asked the stacked wooden blocks to be pulled horizontally on the same ho

In order to explore "which of the wooden blocks and iron blocks with the same bottom area has a rougher lower surface", Xiao Di asked the stacked wooden blocks to be pulled horizontally on the same horizontal plane. (1) Reading the figure, we can see that the calibration value of the spring dynamometer is 0.2N, so in experiment B, the tension F B = 6.6n is measured.

(2) In experiments A and B, the blocks of wood and iron were stacked together to make the pressure in the two experiments the same;

(3) In the two experiments, the pressure on the horizontal plane is the same, the contact surface is different, the tension is different, and F B > F A, so it can be concluded that the lower surface of the wood block is rougher;

(4) In order to compare who has better anti-skid performance between A and B, an experiment can be designed by the control variable method: the same object is pulled by a spring dynamometer to move in a straight line at a uniform speed on the surfaces of A and B tiles, and the greater the pulling force, the better the anti-skid performance.

So the answer is: (1) 6.6; (2) pressure; (3) The lower surface of the block is rough;

(4) Use a spring dynamometer to pull the same object to move in a straight line at a uniform speed on the surfaces of two kinds of tiles A and B. Comparing the magnitude of the pulling force at this time, the greater the pulling force, the rougher the contact surface and the better the anti-skid performance.