**1. The problem statement, all variables and given/known data**

An automobile travels in a straight line for 10 seconds at 20 m/s than accelerates uniformly to a speed of 30 m/s in the next 10 seconds. Find the total displacement.

**2. Relevant equations**

d = 1/2(v_{0}+v)t

**3. The attempt at a solution**

v_{0} = 20 m/s

v = 30 m/s

t = t1 + t2 = 10 sec + 10 sec = 20 sec

d = 1/2 (20 + 30) (20)

d = 500 m

The answer key though says it should be 450 m and I’m not sure why that would be the case…

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