[单选题]
You throw a ball straight up4kigeqz w:*v4 5 rvg9b. Compareb slsdruprn 0, (o6l1vw,.by0 the sign of the work done by gravity while the ball goes up with the sign of the work donbolv0lrs ,d y(su r6.1b0 p,wne by 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
| 
