SOLUTION: a car starting from rest moves with a constant acceleration of 10 mi/hr2 for 1 hour, then decelerates at a constant 5 mi/hr2 until it comes to a stop. How far has it travelled?

Question 941427: a car starting from rest moves with a constant acceleration of 10 mi/hr2 for 1 hour, then decelerates at a constant 5 mi/hr2 until it comes to a stop. How far has it travelled?
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
a car starting from rest moves with a constant acceleration of 10 mi/hr2 for 1 hour, then decelerates at a constant 5 mi/hr2 until it comes to a stop. How far has it travelled?
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s = at^2/2
For the 1st hour, s = 10*1/2 = 5 miles.
It's moving at v = at = 10 mi/hr
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v = a*t
t = 10/5 = 2 hours
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Its average speed for 2 hours is (10 - 0)/2 = 5 mi/hr
s = 5*2 = 10 miles
Total = 15 miles

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