Hanging Mass Connected to Mass on Smooth Table.

[Student3.41]

Homework Statement

Block A has a mass of 4.90 kg and rests on a smooth table. It is connected to Block B which has a mass of 3.50 kg. Block B is released from rest. How long does it take Block B to travel 0.840 m?

Description of figure; Mass A is on the frictionless table. Mass B is attached to Mass A by a string which is being fed through a pully system at the edge of the table.

Homework Equations

F=mg

The Attempt at a Solution

So, I drew a FBD for both masses. With the coordinate system for each mass in the direction of acceleration.

(A) X-direction --> Fn (Normal Force), -WA=mg Y-direction -->T

(B) No forces in the x-direction. T, -WB=mg in the y-direction

Apply Newton 2nd Law (Both Masses)

Mass A: Fy=may ay=0 Fx=max
Fn-mg=0 T=max
Fn=mg

Mass B: Fy=may
mg-T=may

Since acceleration is the same for the two masses I added, T=max and mg-T=may

T=4.90a
(3.50)(9.81)-T=3.50a

4.90a+3.50a=T-T+34.3kg/m/s^2(N)
8.4(kg)a=34.3N

---> a = 4.08m/s^2

So the givens:
a=4.08
x=0.840m
xi=0m

And I am stuck...!

 

[Student3.41]

Nevemind, I got the answer. Forgot Inital Velocity was 0, so I plugged it into an equation solving for time. Thanks!