interest to assist the presenter), and the presenter receives twice this score (

Question

interest to assist the presenter), and the presenter receives twice this score (so it is in the presenter's interest to be as clear and careful as possible). Presenters will be rotated within the assigned lab groups so that each student has the opportunity to serve as presenter at least three times. These scores will also be added, and divided by the total number of available presentation points (typically 120), that fraction will determine 20 points of the overall lab grade. 5. Group B A 30 gram dart is shot directly vertically upward at 9.0 m/s a cork sphere is dropped from 3.0 m above the dart. Find the velocity of the dart-cork system immediately after the collision. Assume the collision is exactly head-on, the dart sticks in the the same instant that a 20 gram cork, and that air resistance is negligible.

Explanation / Answer

velocity of dart = 9 m/sec

So h = 9t

Height of sphere = 3 - 0.5 gt^2

3-4.9t^2 = 9t

t = 0.29 sec

Speed of dart at the time of collision = 9 m/sec upward

Speed of sphere = gt = 9.8*0.29 = 2.84 m/sec downward

Using momentum conservation principle,

30*9 -20*2.84 = (30+20) *v (v in upward direction)

velocity of dart-cock system,v = 4.26 m/sec upward (ans)

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