# Homework Help: Time in acceleration

1. Aug 18, 2009

hello just a quick question, in the experiemental formula for acceleration (2xr/t^2) if the time was in milli seconds e.g 0.00.67 seconds, before u substitute the value in the formula would u need to convert that time to 1 second, by timing everything by 1000 then diving the values by 6.7 to find the acceleration for that 1 second? (m/s ^ -2)

thankyou

2. Aug 18, 2009

and another question in a distance vs tme graph would i need to use a line of best fit or can i use a parabola, because the speed is obviously accelerating

3. Aug 18, 2009

### diazona

Where did you get that formula from? Because it doesn't seem to be correct.

But anyway, if you had a correct formula for acceleration, and you had time in milliseconds, and you had acceleration in meters per second squared, then yes you would have to use a conversion factor from milliseconds to seconds. But if you had time in milliseconds and acceleration in meters per millisecond squared, you would not have to use a conversion factor.

In a distance-time graph, accelerated motion looks like a parabola, not a line. So you could not use a best-fit line.

4. Aug 18, 2009

### kuruman

I don't understand what you mean by line of best fit. You can use a parabola only if the acceleration is constant. Otherwise, you will need to find a mathematical expression for x(t) using the known form of the acceleration and integrating twice. Here it seems that the acceleration is not constant so ...