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ConcepTest 2.10b Up in the Air II<br />
Alice <strong>and</strong> Bill are at the top of a cliff of<br />
height H. . Both throw a ball with initial<br />
speed v 0 , Alice straight down <strong>and</strong> Bill<br />
straight up. . The speeds of the balls when<br />
they hit the ground are v A <strong>and</strong> v B . If there<br />
is no air resistance, which is true?<br />
1) v A < v B<br />
2) v A = v B<br />
3) v A > v B<br />
4) impossible to tell<br />
Bill’s ball goes up <strong>and</strong> comes back<br />
down to Bill’s level. At that point, it is<br />
moving downward with v 0 , the same<br />
as Alice’s s ball. Thus, it will hit the<br />
ground with the same speed as<br />
Alice’s ball.<br />
Alice<br />
v 0<br />
v A<br />
v 0<br />
v B<br />
Bill<br />
H<br />
Follow-up:<br />
What happens if there is air resistance?
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