I dont understand Physical science
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I dont understand Physical science

[From: ] [author: ] [Date: 11-09-15] [Hit: ]
D. an acorn falling from a tree-A. maybe,B. slowing down is an acceleration,C.......
Which of the following shows NO acceleration?

A. a car moving at a constant speed of 55 miles per hour
B. a truck slowing down as it approaches a red light
C. a motorcycle changing speed from 50 miles per hour to 70 miles per hour
D. an acorn falling from a tree

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A. maybe, not enough information
B. "slowing down" is an acceleration, accelerating in the opposite direction as it moves
C. "speeding up" is an acceleration, accelerating in the same direction as it moves
D. Falling with insignificant air drag will end up having an acceleration. Gravity isn't balanced by any force, hence it must cause an acceleration


The only reasonable answer is A. But still, I am not satisfied with that answer.

There is no fact indicating that the road is straight. If the road isn't straight, then there IS acceleration required.
http://en.wikipedia.org/wiki/Acceleratio…

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the answer is A.

Acceleration is about changing speed, answer A is a constant.

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That's probably because you haven't studied.
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