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

If a 1500kg car can accelerate from 35 km/h to 55 km/h in 4.0 s, how long will it take to accelerate from 55 km/h to 75 km/h? Assume the power stays the same, and neglect frictional losses.

**2. Relevant equations**

Converting the velocities to m/s, I got... V1=9.7m/s, V2=15m/s, V3=21m/s

Power = work/time = force*distance/time = mass*acceleration*distance/time

Acceleration1 = (V2-V1)/T1 (which is 4 sec) = 1.3 m/s^2

I'm using d = vt + (1/2)at^2 to find distance <----- This I am not totally sure off...

**3. The attempt at a solution**

So...I did... P=mad/t=ma*(V1t+.5at^2) = 23985

P1 = P2 as the problem stated...

So... a2 = (v3-v2)/t...After substitution I have

a = P / (m*(v3-v2)) = 1.13 m/s^2

Using a = (v3-v2)/t...I solved for t... I got 6.8s

It says I got the wrong answers, but can't figure out there I did it wrong...