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Calculate the minimum stopping distance on wet concrete and dry concrete for a 1526 kg...

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lbawa | Student, Undergraduate | (Level 1) Honors

Posted May 7, 2013 at 12:59 AM via web

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Calculate the minimum stopping distance on wet concrete and dry concrete for a 1526 kg car originally travelling at 25 m/s. (coefficient of kinetic friction for wet concrete=0.5, dry concrete=0.7. 

Answer at the back of text is: Dry concrete =32 m, wet concrete=46 m

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted May 7, 2013 at 4:02 AM (Answer #1)

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You can use the equation of motion and newtons second law of motion in this situation.

`F = ma`

`V^2 = U^2+2aS`

 

When stopping only friction force will act on the car.

For wet concrete

`F = ma`

`-0.5xx1526xx9.81 = 1526xxa`

`a = -4.905`

 

`V^2 = U^2+2aS`

`0 = 25^2-2xx4.905xxS`

S = 63.71m

 

By the same calculation we can get for dry concrete ;

S = 45.5m

 

First answer is incorrect.

 

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