00:01
In this question, by increase the temperature of aluminum bar from 15 degrees celsius to 35 degrees celsius, it will expand by some amount delta l, which is given by this equation.
00:13
And then, after it expand, we want to apply a force at the ends of that bar so that it goes back to its original length.
00:23
So we want to make its length decrease by the same amount it increased.
00:28
But then what we want to do is compensate the thermal expansion by applying a force.
00:35
This means that we want from one side the thermal expansion alpha times l0 times delta t to be compensated by some strength applied on the bar.
00:49
And the delta l because of the strength must be equal to the delta l because of thermal expansion.
00:55
So this must be equals to 1 divided the 1.
00:58
By e times f divided by a times l0.
01:03
As you can see, we can simplify l0 in both sides of this equation...