What are the physics problems involving velocity and acceleration?

[meteoguy04]

Hi,

I'm having trouble with two physics problems.

- Ashley runs 3.0 km in 4.00 minutes. What is her average velocity? The answer is 45 but I can't figure out how to get it.

- A train moving at 15 km/hr takes 1 minute to come to a stop, find its rate of acceleration, its average velocity and the distance it takes to stop.

Rate of Acceleration
--------------------

15/60 = .25

Average Velocity
----------------

Need help finding this

Distance
--------

15/3.6 = 4.16

4.16 m/s
-------- = .069 m/s^2
60s

Thanks!

 

[quantum]

- Ashley runs 3.0 km in 4.00 minutes. What is her average velocity? The answer is 45 but I can't figure out how to get it.

Use the equation
v=d/t
v=3/4

- A train moving at 15 km/hr takes 1 minute to come to a stop, find its rate of acceleration, its average velocity and the distance it takes to stop.

To find your average velocity, use the same equation as I used above (do it yourself this time so you learn.)

 

[meteoguy04]

Thanks quantum!

I got 3/4 = .75 = .75*60 = 45 for the first one...

For the second one I got 15/60 = .25*60 = 15...

Thanks again!

 

[HallsofIvy]

metioguy04: Let me suggest you do something that quantum also did not do: Write the units with the answer!

You asserted that the answer was 45.

Well, no, the answer CAN'T be 45. The answer has to be a speed and 45 is a number, not a speed. That might seem picky but had you written 45 km/HOUR it would have been a heckuvalot easier to see what to do. Since you gave the time in minutes, the natural thing to do is to answer in km/min.

 

[quantum]

LOL! Looked right over that... Sorry.