Two masses are connected by a string which passes over a pulley with negligible mass and friction.One mass hangs vertically and one mass slides on a frictionless horizontal surface.The vertically hanging mass is 6.00 kg and the mass on the horizontal surface is 4.00 kg.The acceleration of the 4.00 kg mass is A) 1.98 m/s². B) 3.92 m/s². C) 5.88 m/s². D) 6.75 m/s². E) 7.84 m/s².

Question

Quizplus · Accepted Answer

Since the pulley is frictionless, we can assume that the tension in the string is the same on both sides. 
Let's call the acceleration of the hanging mass "a". 
Using Newton's second law for each mass:
For the hanging mass: T - m1g = m1a
For the sliding mass: m2a = T
where T is the tension in the string and g is the acceleration due to gravity.
We can eliminate the tension by substituting T = m2a into the first equation: 
m2a - m1g = m1a
Simplifying:
a = (m1/(m1+m2))g = (6/(6+4))9.8 = 5.88 m/s^2
Therefore, our answer is C.

Two Masses Are Connected by a String Which Passes Over