Question about Acceleration.......I'm Confused?

Question

A car can go from 0 to 60 in 3 seconds, how long would it take for the car to go from 0 to 3 mi/h?




Thanks for your help it is VERY much appreciated:)

Answer 1

Hi,
There are a couple ways to look at this, but one way is to remember that the slope of the velocity curve is this:
m = (v2-v1)/(t2-t1)
= 60/3
= 20
Now, we can write a simple equation:
v = 20t
3 = 20t (Substiting 3 for v.)
t = 3/20
= 0.15

Just in case you're not into writing equations, we can also write it as a simple ratio: (In what follows the numbers after t, i.e., t1 and t2 are subscripts, and are part of the name, not numbers in the problem.)
t1/v1 =t2/v2
t1/3 = 3/60
60t1 = 9
t1 = 9/60
= 3/20
=.15 The same as above.

Hope this helps some.
FE

Answer 2

You have to assume a constant acceleration & use the formula v=a*t, where v is velocity, a is acceleration, t is time. First plug in the values you know:

60 mph = a * 3 s

So a= 60mph/3s = 20mph/s

Now that you know a, use it to solve for t:

3 mph = 20 mph/s * t

t = 3mph/(20mph/s) = 0.15 seconds. Voila!

Answer 3

t1/v1 =t2/v2
t1/3 = 3/60
60t1 = 9
t1 = 9/60
= 3/20
=.15