Thermal Deformation

[alejo12]

hi everyone,

Need help understanding the negative sign when using the formula for change in length when experience a temperature change.

The problem I was solving states that a steel beam was subject to a temperature change from -10 to 40 degrees.

The solutions has:

T2=-10

T1=40 ... why ?

If the solution is correct , what should I do with the negative sign ?

will appreciate any help... thanks !

 

[Phalanx]

hi everyone, Need help understanding the negative sign when using the formula for change in length when experience a temperature change.

The problem I was solving states that a steel beam was subject to a temperature change from -10 to 40 degrees.

The solutions has:

T2=-10

T1=40 ... why ?

If the solution is correct , what should I do with the negative sign ?

will appreciate any help... thanks !

You need to know the overall change in temperature to figure out the change in length.

T1 = final temp

T2 = initial temp

Total temp change = T1 - T2 => 40 - (-10) = 40 + 10 = 50 degrees.

Think of it this way: The beam was heated up 10 degrees just to get it back to 0, and now it's being heated up an additional 40 degrees. The problem could have stated T1 = 100 and T2 = 50, but the answer would be the same since the change in temp is still 50.

 

[MA_PE]

like phalanx said all one really cares about is the change in temperature. I doesn't matter what the actual temperatures are. Going from -10 deg to 40 deg represents a 50 deg temperature differential. You'd see the same amount of thermal deformation if the beam had gone from 50 deg to 100 deg.

 

[alejo12]

thanks for clearing that out for me.