- #1

forrestuv

- 10

- 0

## Homework Statement

I need to throw an Object over a fence at a destinationPoint reached in a given time

startPointX=0

startPointY=0.4

destpointX=25

destpointY=0

time=3

fence height=1

fence posX = 10

## The Attempt at a Solution

I decided to split up the problem in two components X,Y

initialSpeedX=(destPointX-startPointX) / time

giving the formula of a falling body:

*distance = 1/2 × gravity × time^2 + intialspeedY × time*

initialSpeedY=((destPointy - startPointy) - (0.5 * gravity * (time* time))) / time

now if I throw the object at an initial velocity of (initialSpeedX,initialSpeedY) it will hit the destpoint in the given time.

now I can calculate if the object at a certain time will hit the fence

timeToReachTheNet = (fencePosX-startPointX) / ((destPointX-startPointx) / Time)

fenceHitHeight = startPointy+( (gravity * (timeToReachTheNet^2) + 2 * initialSpeedY* timeToReachTheNet ) / 2);

if the fenceHitHeight is less than 1 it will hit the fence.

now, if the object hit the fence, how can I find the initialSpeedY so it will reach at least 1mt of height and cross the fence?

it seems that a simple equation is not enough... uhm..

maybe I could find the right equation to directly without the fence hit test..but this is the only method I know :(