Physics help, the answer is D but how do you get it?

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A wire of diameter 0.80 mm is stretched by a force of 40 N. What is the tensile stress in the wire?
A 0.016 MPa
B 0.05 MPa
C 20MPa
D 80MPa

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Eimmanuel

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(Original post by MSMuhammad23)
A wire of diameter 0.80 mm is stretched by a force of 40 N. What is the tensile stress in the wire?
A 0.016 MPa
B 0.05 MPa
C 20MPa
D 80MPa

You just need to apply the tensile stress or stress formula

Spoiler:

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http://physicsnet.co.uk/a-level-phys...stress-strain/

Ensure your conversion of unit is correct (mm to metre).

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MSMuhammad23

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Do you do 0.8^2 * pi * 40 or something else?

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(Original post by MSMuhammad23)
Do you do 0.8^2 * pi * 40 or something else?

No.

What is the formula for stress?

How do you convert mm to metre?

How compute the cross-sectional area of the wire?

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Rehman Mallah

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First you need to know the formula to work out the tensile stress, which is;

$stress = \frac{F}{A}$

Now find the area as you know the Force (half the diameter) :

$r = \frac{0.80}{2} = 0.40$
$A = (0.40 * 10^{-3} )^{2} * \pi$

Now you have the area just find the stress and divide by 10^6 to get it into MPa

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MSMuhammad23

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Thanks for the help bro

(Original post by Rehman Mallah)
First you need to know the formula to work out the tensile stress, which is;

$stress = \frac{F}{A}$

Now find the area as you know the Force (half the diameter) :

$r = \frac{0.80}{2} = 0.40$
$A = (0.40 * 10^{-3} )^{2} * \pi$

Now you have the area just find the stress and divide by 10^6 to get it into MPa

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