( ? (4) Move the schoolbag to the right (or move the rope to the left)

(1) The density of water is known as 1g/cm 3, and the volume of water is 600mL.

The gravity of water.

(2) As shown in the figure;

(3) According to the lever balance power multiplied by the power arm, it is equal to the resistance multiplied by the resistance arm, and if it is, it is obtained.

(4) This end of the schoolbag sinks, indicating that the product of the schoolbag and its arm is too large, so it is necessary to reduce the arm of the schoolbag or increase the arm of the water bottle, or reduce the arm of the schoolbag and increase the arm of the water.