A block is placed on a large horizontal plate. The coefficient of static friction between the block and the plate is μ. The plate is vibrating harmonically with the frequency f in the direction that makes the angle θ = 45° with the vertical. The plate remains horizontal at all times.

Find the minimum amplitude of vibrations A that would make the block:

Our October Challenge, Bar-hopping on a string, received fewer solutions than usual so we are especially pleased to recognize the successful solvers:

Phil Cahill (The SI Organization, Inc., Rosemont, PA)

Norman Derby (Southwestern Oregon Community College, Brookings, OR)

Franky A. M. Lumbantobing (STKIP Surya, Tangerang, Indonesia)

A. John Mallinckrodt (Cal Poly Pomona, Pomona, CA)

Matthew W. Milligan (Farragut High School, Knoxville, TN)

Carl E. Mungan (U. S. Naval Academy, Annapolis, MD)

Pascal Renault (John Tyler Community College, Midlothian, VA)

Randall J. Scalise (Southern Methodist University,...

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