# Projectile Motion Practice - An arrow launched and land at different points. HELP

1. Sep 24, 2015

### Marvels

1. The problem statement, all variables and given/known data

An Arrow is shot from an initial velocity of 45 m/s 52 degrees above the horizontal. It lands on a 5 m high roof of a house. The arrow is shot from a height of 1.5 m.

(v) Would it be able to pass over a 50 m high tree located 75 m away?
(vi) What is its' total time of flight?
(vii) How far away is the house?

2. Relevant equations

d = vit +1/2at^2
v=d/t
a = vf-vi/t

3. The attempt at a solution

I've calculated the max height of the arrow; 65.43 m, and the time, 3.6 s.

I don't know how to calculate the horizontal displacement of an object starting 1.5 m off the ground.

2. Sep 24, 2015

### SteamKing

Staff Emeritus
How does the starting height affect the horizontal displacement? What would happen to the arrow if you moved the ground up 1.5 m?

3. Sep 25, 2015

### Marvels

Do I add 1.5 m to the regular displacement? (Do I do the same with y disp, too?)

4. Sep 25, 2015

### haruspex

No, why do you think that might be valid? Please don't make wild guesses.
What you can do is make shift of origin, provided you do it consistently. I.e. add or subtract a number from all horizontal coordinates, and likewise (but maybe a different number) from all heights.