1.3.10. A 
mass and a 
mass are linked by a light string passed over a frictionless pulley. Calculate the acceleration of the system.
Extracted from B. Kennedy. (2001). Higher Physics Progressive Problems.
Solution.
At first glance, as mass 
is heavier than mass 
, one can expect that the heavier mass will fall down and the lighter mass will move up.
Draw the free body diagram of each mass below:
Write the equation of motion for both masses:
Both masses and will accelerate with a magnitude of 
.