[单选题]
You throw a ball straight up.yjrgh *:a na-9+ kz7gyk.alw-eyh1r4 Compare the sign of the work done s6qp lo3y :a+v/euvm4 by gravity while the ball goes up with the sign of the work done bey p6:lv v3s4q/ u+aomy gravity while it goes down.
A. Work is + on the way up and + on the way down.
B. Work is + on the way up and - on the way down.
C. Work is - on the way up and + on the way down.
D. Work is - on the way up and - on the way down.
参考答案: C
本题详细解析:
暂无
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