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February 13th, 2010, 08:10 PM   #1
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The distance, d m, in which a train can be stopped by its brakes varies partly as the speed, v km/h, and partly as the square of the speed. When running at 10 km/h the train can be stopped in 45 m, and at 20 km/h in 140 m. Find the formula for d in terms of v.
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February 13th, 2010, 11:05 PM   #2
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Re: Variations...

What it means is that the distance function for a given speed, d(v), is something of the form av≤+bv, and you have to find constants a and b.

d(10)=45, so 100a+10b = 45
d(20)=140, so 400a+20b = 140

Solve the two simultaneous equations to get a and b.
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