projectile motion

用戶93130

2013-09-15 6:56 pm

An aeroplane carrying out a parcel drop releases a parcel while traveling at a stead speed of 90m/s at an altitude of 200m. Calculate:
a) the time between the parcel leaving the aeroplane and it striking the ground
b) the horizontal distance travelled by the parcel in this time
c) the speed at which the parcel strikes the ground

回答 (1)

天同

2013-09-15 8:41 pm

✔ 最佳答案

(a) Consider the vertical motion only.
Use equation: s = ut + (1/2)at^2
with s = -200 m, u = 0 m/s, a = -g (=-10 m/s^2), t = ?
hence, -200 = (1/2).(-10)t^2
t = 6.325 s

(b) Horizontal distance travelled = 90 x 6.325 m = 569 m

(c) Use equation v = u + at to calculate the vertical velocity before striking the ground, with u = 0 m/s, a = -g (=-10 m/s^2), t = 6.325 s, v =?
thus, v = 10 x 6.325 m/s = 63.25 m/s

Let V be the speed before striking the ground
hence, V^2 = 90^2 + 63.25^2
V = 110 m/s

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