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## Homework Statement

Three identical blocks connected by ideal strings are being pulled along a horizontal frictionless surface by a horizontal force F_vec. The magnitude of the tension in the string between blocks B and C is [tex]T = 3.00 {\rm N}[/tex]. Assume that each block has mass [tex]m = 0.400 {\rm kg}[/tex].

a)What is the magnitude F of the force?

b) What is the tension T_AB in the string between block A and block B?

http://img340.imageshack.us/img340/3789/9374t.jpg [Broken]

## Homework Equations

W=mg

F=ma

## The Attempt at a Solution

a) i made A and B as one object and calculated the acceleration of the object

two forces are acting on this object.

1st force

w=mg

w=0.4*9.8

W=3.92N

2nd force is tension = 3N

Found Fnet to be 3+3.92+4.94

Fnet = 11.86

used F=ma formula

a=11.86/0.4

a=29.65m/s^2

then to find the force i went: a=Fnet/3m

so a=11.86/3*0.4

a=9.88m/s

To find force i use 9.88 * 0.4 = 4N ------> answer's says it 4.50N (tell me where i have gone wrong)

b) Used f=ma

f= 29.65 * 0.4

=11.86 i know this is incorrect, but someone tell me the correct way of doing this.

P.S

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