Two Blocks Rest on a Horizontal Frictionless Surface as Shown

question 2

Multiple Choice

Two blocks rest on a horizontal frictionless surface as shown. The surface between the top and bottom blocks is roughened so that there is no slipping between the two blocks. A 30-N force is applied to the bottom block as suggested in the figure.
-What is the minimum coefficient of static friction necessary to keep the top block from slipping on the bottom block?

• A)0.05
• B)0.10
• C)0.20
• D)0.30
• E)0.40