Calculate acceleration of the 4 kilogram block

[sobek]

Homework Statement

Three blocks of masses 1.0, 2.0, and 4.0 kilograms are connected by mass less strings, one of which passes over a frictionless pulley of negligible mass, as shown above. Calculate each of the following.
a. The acceleration of the 4 kilogram block
b. The tension in the string supporting the 4 kilogram block
c. The tension in the string connected to the l kilogram block

(Sorry but I can't seem to get the pic on here- basically on one side of the pulley is a 4kg mass, and on the other side is a 2kg mass that is connected by a string to a 1kg mass)


I don't really know where or how to start. I know I'll need to use Newton's Second Law. But I'm have difficult applying it to these problems.

Thank you

 

[rl.bhat]

Three masses are connected by two stings.
All the masses move with the same acceleration.
Let tension in the string connecting 4 kg and 3 kg be T1, and tension in the string connecting 2 kg and 1 kg be T2.
For 4 kg, 4*g - T1 = 4*a.
Similarly write the other two equations for 2 kg and 1 kg. Then solve the equations to find T1, T2 and a.