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?

 

[Moetasim]

t = ? [i dunno!]

Yes, that is correct. We know that the ball takes off at a 30-degree angle, so we can use trigonometry to determine the initial vertical and horizontal velocities. However, we would need more information such as the speed or distance the ball was thrown to calculate these values. We also know that the acceleration due to gravity is 9.8 m/s^2 and it acts in the downward direction, so it would be negative. Without knowing the time or any other information, we cannot fully solve this problem.