The acceleration of a particle on a horizontal xy plane is given by a = 4t i + 5t j, where a is in meters per second-squared and t is in seconds. At t = 0, the particle has the position vector r = (20.0 m) i + (40.0 m) j and the velocity vector v = (5.00 m/s) i + (2.00 m/s) j. (a) What is the position vector of the particle at t = 9.00 s? r = ( m) i + ( m) j This isn't a homework problem, but a example problem I'm trying to figure out for my test study guide. I've tried several ways, but can't seem to figure out the correct way at all. Any help to get me started would be great. Thanks.