1. Apr 13, 2010

### phisics99

1. The problem statement, all variables and given/known data
A radius vector of a particle varies with time t as r=at(1-$$\alpha$$t) where "a" is a constant vector $$\alpha$$ is a positive factor.
Find:
a) velocity "v" and the acceleration $$\omega$$ as function of time;
b) the time interval $$\Delta$$t taken by the particle to return to the initial points and the distance "s" covered during this time.

I have solved a) and have problem with b)

2. Relevant equations

r=at(1-$$\alpha$$t)
v=a(1-2$$\alpha$$t)
$$\omega$$=-2$$\alpha$$

3. The attempt at a solution
To find time I should divide r/v? I don't understand that. The result is: t=1/$$\alpha$$.
Now how find distance? Substitute founded time to equation as r?
Looking for some help, my phisical english isn't so good , because come from Poland. Thx

2. Apr 13, 2010

### tiny-tim

Welcome to PF!

Hi phisics99! Welcome to PF!

(have an alpha: α and an omega: ω )
(btw, your ω is missing an α )

To find time, just use the original equation, r = at(1 - αt) …

r = 0 at t = 0 and at t = … ?

(and then use one of the standard constant acceleration equations to get distance)