# Horizontal range questions help

## Homework Statement

A ball rolls off a table at an initial velocity of 2.5 m/s. The table's height is 3 meters. Similarly another question asks for the same thing except this time it's a rifle shooting a bullet with a velocity of 250 m/s with a height of 3 meters.

## Homework Equations

The formula I have is this: sqrt(2*height divided by 9.8)

## The Attempt at a Solution

I got the same answer for both because the height is the same but their velocities are radically different. Do they not factor into the formula?

CWatters
Homework Helper
Gold Member
No...because the vertical component is zero in both cases.

No...because the vertical component is zero in both cases.
So my answer would be the same for the two questions?

CWatters
Homework Helper
Gold Member
Probably, but you don't actually state the full question. Are they asking about the velocity the ball hits the ground? The time taken to hit the ground? How high it bounces? Sure I could work it out from the equation you use but how can I tell if you are using the right equation?

Do you understand why you are using that equation and not one that includes the horizontal velocity? Many of the equations of motion include the initial velocity. What is the relevant initial velocity in this case?

Edit: I might be totally wrong. The question title talks about horizontal range? Is that what the question asks you to calculate?

Edit 2: sqrt(2*height divided by 9.8) = ???

CWatters
Homework Helper
Gold Member
Perhaps I'm being too cryptic.

You quote the equation "sqrt(2*height divided by 9.8)". What does that give you?

Probably, but you don't actually state the full question. Are they asking about the velocity the ball hits the ground? The time taken to hit the ground? How high it bounces? Sure I could work it out from the equation you use but how can I tell if you are using the right equation?

Do you understand why you are using that equation and not one that includes the horizontal velocity? Many of the equations of motion include the initial velocity. What is the relevant initial velocity in this case?

Edit: I might be totally wrong. The question title talks about horizontal range? Is that what the question asks you to calculate?

Edit 2: sqrt(2*height divided by 9.8) = ???
Yeah, I'm looking for the horizontal range and how long it spends in the air. I have .78 as the answers. That would mean the horizontal range is 1.56, right?

CWatters