Question

A playground is surrounded by a fence 2.0 m high. A boy who plays in the
playground kicks a ball vertically upward from a height of 0.2 m with a speed of
10 m/s. How much time does the ball spend above the height of the fence?
(

Answer 1

a=-g

v=-gt+v0

when t=0, v=10
v=-gt+10

x=-g/2 t^2+10t+x0

when t=0, x=0.2
x=-g/2 t^2+10t+0.2

when x=2
2=-g/2 t^2+10t+0.2
0=-g/2 t^2+10t-1.8
0=t^2-20/g t+ 3.6/g
0=t^2-2.04t+0.37

Using the quadratic rule, t=0.20 and t=1.84

So the ball stays in the air for 1.64 seconds.

Answer 2

i can never remember the physics equation and always resort to the parabola :/

Answer 3

that is the parabola :) yay!!