INTERACTIVE EXAMPLE
© Copyright, Department of Physics, University of Illinois at Urbana-Champaign
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2 Masses on a Table Edge



Two blocks are positioned as shown above, and are released from rest. Block A with mass MA=40 kg can slide on the table without friction. Block B has mass MB=20 kg. The two blocks are connected by a massless string of length 2 meters passing over ideal pulley. An 'ideal' pulley is frictionless and massless. The 'massless string' also cannot stretch or shrink. These simplifying assumptions allow us to focus on fundamental aspects of the problem without getting bogged down with (less fundamental) details. Perhaps you've heard the expression 'Let's take a spherical cow'! Assume that there is no friction anywhere in the system. Positive directions of x-axis and y-axis are indicated by the arrows.

Given the magnitude and sign of gravitational acceleration g= 9.8 m/sec2, what is the sign and magnitude of acceleration aB of block B, as long as block A remains on the table?

aB = m/s2