Youngs modulus - stress- check please - easyish

[pat666]

Homework Statement

A steel beam is used in the road bed of a bridge. The beam is mounted between two concrete supports when the temperature is 23⁰C, with no room for thermal expansion. What compressional stress must the concrete supports apply to each end of the beam, if they are to keep the beam from expanding when the temperature rises to 42⁰C?
Assume: Co-efficient of linear expansion for steel = 11 x 10-6K-1
Young’s modulus for steel = 210GN.m-2

Homework Equations

stress = F/A=Y deltaL/L
deltaL/L=alpha deltaT

The Attempt at a Solution

I got 0.04389N/m^2
the reason i out this up is that the compressional stress i found seem very small?

 

[PhanthomJay]

Are your units of temperature (degrees K or degrees C) consistent?

 

[RTW69]

You have an exponent error somewhere. Remember Giga is 10^9. Check you math.

 

[pat666]

Celsius

 

[pat666]

rtw69 there is no giga anything in the question, what do you mean? what answer did you get??

 

[PhanthomJay]

Oh sorry, the coef of expansion per degrees K is the same as the coef of expansion per degrees C. As RTW69 noted, don't forget the G (Giga) as in Y = (210)(10)^9 N/m^2

 

[pat666]

ohhhhhhhh ok i didnt even see that big G sitting there... thanks is your answer apart from the index the same as mine?

 

[PhanthomJay]

ohhhhhhhh ok i didnt even see that big G sitting there... thanks is your answer apart from the index the same as mine?

Yes.