1. The problem statement, all variables and given/known data A pebble of mass m rests on the block of mass of m2 the ideal Atwood's machine in the figure below. Find the force exerted by the pebble on the block of mass m2. (Use the following variables as necessary: m for m, m_1 for m1, m_2 for m2, and g for gravity.) 2. Relevant equations 3. The attempt at a solution i dont' know where to begin- -help!