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minimum stopping distance

 
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flores101



Joined: 28 Feb 2011
Posts: 1
Location: canada

PostPosted: Mon Feb 28, 2011 1:52 am    Post subject: minimum stopping distance Reply with quote

A load of steel of mass 6,235 kg rests on the flatbed of a truck. It is held in place by metal brackets that can exert a maximum horizontal force of 7,974 N. When the truck is traveling 20 m/s, what is the minimum stopping distance if the load is not to slide forward into the cab?
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hepcj
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Joined: 23 Jun 2007
Posts: 125

PostPosted: Thu Mar 03, 2011 6:51 pm    Post subject: Reply with quote

This question requires that you know that force is the rate of change of acceleration and the equations of linear motion. You know maximum force before the brackets will break and the mass of the steel they are stopping from moving. So using
F = m a
you can calculate the acceleration a. In this case it is a deceleration so it is given a negative sign.

Then using the equations of motion to calculate the time taken to stop.

v= u + a t.

Where v is the final velocity i.e. = 0 m/s and u is the initial velocity = 20 m/s

From this you can calculate the time t.
Finally, to find the stopping distance s substitute the known information in

s = u t + 1/2 a t^2

and this will give you stopping distance.

I got an answer of 156 m (156.4)
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