What Forces Act on Three Blocks on a Frictionless Surface?

[ScullyX51]

Homework Statement

Three identical blocks connected by ideal strings are being pulled along a horizontal frictionless surface by a horizontal force F_vec. (Intro 1 figure) The magnitude of the tension in the string between blocks B and C is T = 3.00 N. Assume that each block has mass m = 0.400 kg

What is the magnitude F of the force?
What is the tension T:AB in the string between block A and block B?

Homework Equations

F=ma

The Attempt at a Solution

I am unsure of how to approach the first part of the problem. For the second part, since t is the only force acting this the block,
I have: T=ma
I solve for A from the first part of the equation where t is given as follows:
t=ma
3=.400a
a=3/.4
a=7.5 m/s^2

I plugged this into to solve for the other tension as follows:
t=ma
t=.4*7.5
t=3

Mastering physics is saying the tension and the acceleration is wrong. Where did I screw up?

 

[LowlyPion]

What is the order of your blocks?

T <---{A}--{B}--{C}

Generally, whatever your force is, the acceleration will be F/(3*m) and then the intermediate tensions would be whatever force is needed to keep the blocks remaining moving with that acceleration.

In the example above that would be 2/3*F between A:B and 1/3*F between B:C

 

[thomate1]

As a scientist, it is important to carefully analyze the given information and equations in order to solve a problem accurately. In this case, the given information states that the force F is being applied to the three blocks, and the tension T is between blocks B and C. The first part of the problem asks for the magnitude of the force F, which can be found using the equation F=ma. Since the mass of each block is given as 0.400 kg, the total mass of the system is 3*0.400=1.2 kg. Therefore, the force F can be calculated as F=ma=(1.2 kg)(a). However, we do not have enough information to solve for a, so we cannot accurately determine the magnitude of F.

For the second part of the problem, the tension T:AB is being asked for. Since the blocks are identical and connected by ideal strings, the tension throughout the system is constant. Therefore, the tension between block A and block B is also 3.00 N. This can be seen by considering the forces acting on each block. Block A has a tension force T:AB acting on it towards the right, and block B has a tension force T:AB acting on it towards the left. These forces are equal in magnitude and opposite in direction, resulting in a net force of 0 on block A and B. Therefore, the tension T:AB must also be 3.00 N.

In conclusion, it is important to carefully analyze the given information and equations in order to accurately solve a problem. In this case, the given information was not sufficient to determine the magnitude of the force F, but we were able to determine that the tension T:AB is equal to 3.00 N.