physics
posted by Amy .
1)Topfuel drag racers are able to uniformly accelerate at 12.3 m/s2 from rest to 98 m/s before crossing the finish line. How much time elapses during the run?
2)A racecar accelerates from rest at +7.2 m/s2 for 4.1 seconds. How fast will it be going at the end of that time?
3)A bullet accelerates at 6.8 X 10^4 m/s2 from rest as it travels the 0.80 m of a rifle barrel. What is the velocity of the bullet as it leaves the barrel?

v = 0 + a*t
98 = 12.3 * t
solve for t
v = 0 + a*t again
x = X0 + Vo t +.5 a t^2
.8 = 0 + 0 + (.5) (6.8*10^4 )t^2
t^2 = 2.35 10^5
t = .00485 seconds in barrel
then use
v = o + a t again 
A bullet accelerates at 6.8*10^4 m/s^2 from rest as it travels the 0.80 m of the rifle barrel. How long was then bullet in the barrel? What velocity does the bullet have as it leaves the barrel?
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