Projectile Motion: An Arrow Shot & Landed at Different Points

Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
3 replies · 2K views
Marvels
Messages
6
Reaction score
0

Homework Statement



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?

Homework Equations



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

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.
 
Physics news on Phys.org
Marvels said:

Homework Statement



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?

Homework Equations



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

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.

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

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