1 answer
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find acceleration: a=changev/time=35/5=7m/s^2
avg speed during acceleration, deacceleration= 17.5m/s
Now, how far does it go accelerating/deaccelerating? distance=17.5*5m=87.5m , and then again 87.5m slowing down.
so it must go 450-35 m at constant speed, for 35 seconds.
max speed=(450-175)/35 = you do it.