If a car can go from 0 to 60mi/hr in 8.0 seconds, what would be its final speed after 5.0 seconds if its starting speed were 50mi/hr? My answer was -10, is this correct. If not , I need help

Answer 1

How ever did you get a negative number? I'd assume we are using the same positive acceleration, starting from 50 mph!

assuming constant acceleration, then since the velocity changed by 88ft/s in 8 seconds,

a = 11 ft/s^2

Now to find v, just recall that

v(t) = Vo + at
Just plug in your numbers. I guarantee you will not wind up with -10.

Of course, in the real world, acceleration from a standing start is very different from a starting speed of 50 mph!

Answer 2

oops, didn't find acceleration first(7.5), which is 60 /8. Then 7.5 x 5 + 50=87.5,
a*t+v(starting speed)=final speed