Finding the Position of a Particle at the Instant it Changes Direction

[bearhug]

A particle moves along the x axis. Its position is given by the equation x = 1.90 + 3.10t - 4.15 t2 with x in meters and t in seconds. Determine its position at the instant it changes direction.

When I'm reading this problem I picture a parabola and the instant the particle changes direction is at the maximum. However I'm not sure that is right and am having trouble figuring out how to use the quadratic equation to find the position. I was thinking that when the position changes it goes from positive to negative is that right?

Any help would be greatly appreciated

 

[dmoravec]

have you done basic calculus? If you had you could take the derivative of your position equation and get an equation for velocity. When it changes direction the velocity will be 0. From there you can get a t value to plug back into the position equation.

 

[bearhug]

Oh yeah I didn't even consider that thanks for pointing that out.