[单选题]
An object of mass m rests on a rough surface. Another object of mass M is connected to it via a frictionless pulley. The coefficient of dynamic friction between the surface and the object of mass m is μ.
When the object of mass M is released, the objects accelerate. What is the acceleration of the system?
A. $\frac{gM}{M+m}$
B. $\frac{gm}{M+m}$
C. $\frac{gm-{\mu}m}{M+m}$
D. $\frac{{\mu}m-gm}{M+m}$
参考答案: C
本题详细解析: The resultant force is the difference between the weight of the object of mass M and the force of friction between the object of mass m and the rough surface.
