a car initially traveling at 15 m/s accelerates at a constant rate of 4.5 m/s^2 over a distance of 45m.?

Question

How long does it take the car to cover this distance? What equation should i use and how can i show my work? Thanks to all who answer!!!

Answer 1

I'm starting to suspect that there are high school students out there just trying to get their homework done the easiest way. I can appreciate that. Now there is a basic motion equation you should have an idea about and realize it can be used in different ways to solve problems with different knowns.

Well actually there may be a few, the key is understanding how one leads into the other. Miss one of those links and you can become quite confused and make further learning more challenging. It doesn't hurt to review. And it doesn't hurt getting out on a saturday night.

I think the equation you want is:

1/2at^2+v1t=d a good way to confirm this is the right equation is to verify that all the units are the same.

so you know:
v1=15m/s
a=4.5m/s^2
d=45m
and we're trying to calculate t. Looks like we're going to have a quadratic equation after moving things around:

1/2(4.5)t^2+15t-45=0

So if you remember math from maybe last year we have to solve this quadratic equation. Now that is another question if you do not know how to solve a quadratic question.

Answer 2

Show your work carefully and mark your answer clearly.
To find t: x=vo*t + 1/2 at^2
vo=15 m/sec
x=45 m
a=4.5 m/sec^2
Substitute in the numbers. After shuffling the equation about, you will have a quadratic in t, which you solve and discard the spurious root.

Answer 3

d= 4.5/2t^2+15 t
so 45 = 2.25 t^2 +15 t
now solve this 2nd degree equation and take the positive solution