A Mass M Slides on a Horizontal Surface

Multiple Choice

A mass M slides on a horizontal surface.A mass m is attached to a string routed over a pulley as shown below.Friction is present.When m is released,M accelerates to the right.The coefficient of friction between M and the surface is µ_k.Which one of the following statements is true?

A) Doubling the mass of m will double the acceleration.
B) Doubling the mass of M will halve the acceleration.
C) µ_k will increase as mass M accelerates.
D) Doubling the mass of M will double the force of friction.
E) Doubling the mass of M will double µ_k.