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Baoshan district junior high school mathematics Moore
A, because the mechanical energy of the object doing negative work is reduced by forces other than gravity and spring elasticity, the absolute value of the slope of the E-x image is equal to the magnitude of the tensile force on the object. As can be seen from the figure, the absolute value of the slope increases gradually in O ~ S 1, so the tension on the object increases gradually in O ~ S 1. So, A is wrong.

B, because the absolute value of the slope of the E-x image of the object in S 1 ~ S2 is unchanged, the tensile force on the object is unchanged. If the tension is equal to the gravity on the object, the object moves in a straight line at a uniform speed. Therefore, B is correct.

C, because the object in S 1 ~ S2 has the same tension and acceleration, it is impossible for the object to move in a straight line with variable acceleration, so C is wrong.

D. If the pulling force of the rope on the object is less than the gravity of the object in the range of 0 ~ S2, the object will move downward with acceleration, so the kinetic energy of the object will increase continuously, so D is correct.

So choose b and d.