How to find the force that has to be pulled to a set of two blocks given the condition that a wire can break?

Jun 2017
337
6
Lima, Peru
The problem is as follows:

Two identical blocks are joined by a wire over a horizontal table. Assume the friction between the table and the blocks is negligible. The wire can bear a maximum tension of $6\,N$. If the two block are pulled by a Force as a function of time t given in seconds. Find the instant (in seconds) when the wire breaks.



The alternatives are as follows:

$\begin{array}{ll}
1.&4\,N\\
2.&5\,N\\
3.&6\,N\\
4.&8\,N\\
5.&10\,N\\
\end{array}$

In this problem I'm still stuck at exactly how should I use the fact that I'm given the maximum tension of the wire between the conecting blocks.

The only thing which I could spot is that the Force is a function of time as follows:

$F(t)=2+2t$

If I were to use the tension which is in tandem for the two blocks would be as follows:

$T=ma$

$F-T=ma$

Therefore:

$F=2ma$

But I don't really know how can I connect one information with another. Can someone help me here?. I'm confused exactly what should I do.
 

skeeter

Math Team
Jul 2011
3,266
1,766
Texas
the problem asks for time the wire breaks

all the answer choices are in Newtons ... ?

that time would be 5 sec