4. A 10 kg block on a level surface is pushed by a 50 N force directed 30 degrees below the horizontal (like this: ). The coefficient of static friction between the block and the surface is 0.60 and the coefficient of kinetic friction is 0.40. a. Does the block slide or stay put? Justify your answer with a calculation. b. If it slides, calculate its acceleration. If it stays put, calculate the friction force acting on the block. Show your work.

Two blocks, A and B, are connected by a rope. A second rope is connected to block B and a steady, horizontal tension force of T=50 Newtons is applied. The system moves at a constant speed across the ground. Block B experiences a friction force of 10 Newtons. A.Draw and label an appropriate force vector diagram for block B.  B.What is the friction force acting on block A?

B7

Use the figure to answer the following questions.   A magnet of mass 5.58 kg is suspended from the ceiling by a cord as shown. A large magnet is somewhere off to the right, pulling on the small hanging magnet with a constant force of F = 152.5 N. At what angle theta ?with respect to the vertical does the magnet hang?   a. 70.3 degrees   b. 19.7 degrees   c. 54.0 degrees   d. 59.0 degrees Consider the same situation as in the previous problem. This time the magnet has mass 6.70 kg and the force pulling the magnet to the right has magnitude 99.9 N. What is the magnitude of the tension force in the cord?   a. 199.6 N   b. 292.2 N   c. 119.6 N   d. 165.6 N