A balloon is moving upwards with a uniform velocity of 5ms^-1 .When it is at a height of 400m above the ground, a mass is dropped from it.
(a) How long does the mass take to hit the ground?
(b) What is the velocity when the mass hit the ground?
thanks
al physic
2009-09-27 9:31 pm
回答 (1)
2009-09-27 10:20 pm
✔ 最佳答案
a. When the object is being dropped, it's velocity is 5 m/s, upward.Take upward be positive.
By s = ut - 1/2 gt2
-400 = (5)t - 1/2 (10)t2
Time, t = 9.46 s
b. By v = u - gt
v = 5 - (10)(9.46)
Velocity, v = -89.6 m/s
參考: Physics king
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