Physics motion

👨🏻‍🏫 學術台其他 - 科學

Anonymous

2012-09-29 9:11 pm

You throw a glob of putty straight up toward the ceiling, which is 3.00m above the point where the putty leaves your hand. The initial speed of the putty as it leaves your hand is 9.00m/s .

1. What is the speed of the putty just before it strikes the ceiling?

2. How much time from when it leaves your hand does it take the putty to reach the ceiling?

更新1:

天同: Ans in (1) is wrong but (2) is correct.

回答 (1)

天同

2012-09-29 9:30 pm

✔ 最佳答案

1. Use equation: v^2 = u^2 + 2a.s
with u = 9 m/s, a = -g(=-10 m/s^2), s = 3 m, v =?
hence, v^2 = 9^2 + 2.(-10).(3)
v = 4.58 m/s

2. Use equation: v = u + at
with v = 4.58 m/s, u = 9 m/s, a =-g(=-10 m/s^2), t =?
hence, 4.58 = 9 + (-10)t
t = 0.442 s

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