Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
Trending News
A question on projectile motion?
A cannon is fired at an angle of 30 degrees above the horizontal from a cliff that is 20m above a flat river bottom. What is the initial speed of the projectile if it is found to land 40m from the base of the cliff?
Thanks!
Can anyone kindly explain why Julian made y a 0? Thanks again!
2 Answers
- JulianLv 69 years agoFavorite Answer
Vi = initial speed
g = 9.8 m/s²
x = (Vicos30)t ==>40 = (Vicos30)t ==> t = 40/(Vicos30)
y = 20 + (Visin30)t - gt²/2
------------
0 = 20 + (Visin30)40/(vicos30) - 9.8(40/(Vicos30))²/2
0 = 20 + 40tan30 - 7840/(Vicos30)²
Vi = 15.57m/s ==> answer
# the vertical distance y = 0 because the horizontal distance 40 m is obtained at the river level ==> y = 0
- Anonymous9 years ago
Are you given a time?
Source(s): Me