## anonymous 5 years ago A student standing on the ground throws a ball straight up. The ball leaves the student's hand with a speed of 19.0 when the hand is 2.10 above the ground. How long is the ball in the air before it hits the ground?

1. JamesJ

Ok, what's the equation of motion here? Let u = initial velocity s = initial position g = acceleration due to gravity. Then let y(t) be the position of the particle at time t, and v(t) its velocity at time t in the y direction. We have that $v(t) = u - gt$ and $y(t) = s + ut - \frac{1}{2}gt^2$ Now use that and the data given your equation to find the time t for which y(t) = 0; because that is when it reaches the ground.

2. anonymous

thank you