How Do You Set Up a Physics Problem Involving Projectile Motion?

[lifeisamazing]

The ball takes off at 30deg and lads 40 ft from there.
[Don't solve/calculate the problem, just set up axes, and make a list of what you know or don't: delta-x, delta-y, horizontal velocity, initial vertical velocity, v sub-y, a sub-y, and t.]

is this correct?:
delta-x = 40 ft
delta-y = 0
horizontal velocity = unknown
initial vertical velocity = ? [i dunno!]
v sub-y = ? [i dunno!]
a sub-y = 9.8 [is it positive or negative gravity?]

 

[tiny-tim]

Welcome to PF!

The ball takes off at 30deg and lads 40 ft from there.

initial vertical velocity = ? [i dunno!]
v sub-y = ? [i dunno!]

Hi lifeisamazing! Welcome to PF!

Let's see: do you know delta-y … does the problem specifically say that the ball starts on the ground?

(A ball usually starts by being thrown from someone's hand, several feet higher than it lands!)

v sub-y is the initial vertical velocity, isn't it?

Do you know any relationship between the horizontal velocity and the initial vertical velocity?

a sub-y = 9.8 [is it positive or negative gravity?]

Careful! The distance are in feet, so the figure for gravity must be … ?

As for positive or negative … which direction is it acting in?