sac help please

[götze]

a cylinder steel rod is 1m long and 1.0 cm in radius is being stretched by a load of 800kg
(a) find tensile stress in rod

[pi]

Just a reminder that as this question has been flagged as a "SAC question" (and thanks for your honesty!), please don't give the answer.

Feel free to provide tips, advice, etc.

[götze]

I mean this is a practice sac question .....

[götze]

should have put practice at the front my bad

[Phy124]

The normal stress on an object is given by:



Where is the normal force exerted on the cross sectional area, , of the object.

In this case the cross sectional area is the circular area at the end of the cylinder, given by .

The object is being stretched hence the force is tensile and is thus positive.

The force is the gravitational force exerted by the mass pulling/stretching it downwards.

The force exerted by a mass due to gravity is given by .

Try and take it from here

[götze]

Could you please help me out with the question i know its force/cross sectional area and that force would equal 8000/pi times 0.005^2 but the awnser says 2.55 times 10^7

[Phy124]

It appears you are taking the radius as 0.005, why?

The radius was given as 1cm, so you would either take and have units of a/cm^2 or and have units of a/m^2, where a is dependent on the units used for the force.

N/m^2

[götze]

my bad i was thinking  that was the diameter for some reason cheers for the help

[götze]

N/m^2
[/quote]

How do people write like this is  an app or ?

[alondouek]

LaTex code! You should see a 'pi' symbol with a white background above the writing space. You can use it to write equations and the like.

I found this useful: http://www.artofproblemsolving.com/Wiki/index.php/LaTeX:Commands