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Neijiang three-mode mathematics examination paper
Force analysis of object B, including gravity G, supporting force N and sliding friction F, as shown in the figure.

Then, the force analysis of the object A shows that there may be a static friction force F static between the ground and A due to the gravity Mg, the supporting force FN of the ground, the pressure N' of B against A, and the friction F' of B against A, so it is assumed to be static at first and to the right, as shown in the figure.

When the object B slides at a uniform speed, according to the point force balance condition, there are

mgsinθ-f=0①

N-mgcosθ=0②

When object b slides down at an accelerated speed, there are

mgsinθ>f③

N-mgcosθ=0④

When object B slows down and slides down, there are

mgsinθ