Objectives Pecina
y
01:Posttest 01:Motion Along a Straight Line
eration
1. An elevator moving down passes its neighbor, an elevator moving up. Their speed relative to one another is 8 m/s. What is the velocity of each
elevator relative to someone standing on the first floor? Assume that the elevators are traveling at the same speed, and that the upward direction is
positive.
tant Acceleration
O Both elevators are moving at 8 m/s.
y Falling Objects
O One elevator is moving at 4 m/s; the other elevator is moving at -4 m/s.
O Both elevators are moving at 4 m/s.
tive Velocity
O One elevator is moving at 8 m/s; the other elevator is moving at -8 m/s.
Posttest
on in a Plane
ton's Laws of Motion
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blications of Newton's
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11:53 PM
4/4/2021

B

Explanation: Given that an elevator moving down passes its neighbor, an elevator moving up. Their speed relative to one another is 8 m/s. What is the velocity of each elevator relative to someone standing on the first floor? Assume that the elevators are traveling at the same speed, and that the upward direction is positive.

O Both elevators are moving at 8 m/s.

y Falling Objects

O One elevator is moving at 4 m/s; the other elevator is moving at -4 m/s.

O Both elevators are moving at 4 m/s.

tive Velocity

O One elevator is moving at 8 m/s; the other elevator is moving at -8 m/s.

Solution.

Since the upward direction is positive, the downward direction will be negative.

For their speed relative to one another to be 8 m/s, the individual velocity will be:

4 - ( - 4 ) = 8

Therefore, the correct answer is:

One elevator is moving at 4 m/s; the other elevator is moving at -4 m/s

Which is option B

Because the negative sign multiply by negative sign will give positive.

That is,

4 + 4 = 8

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