用绳子系一物体,在竖直平面内作圆周运动,当这物体达到最高点时,(1)有人说:“这时物体受到三个力:重力、绳子的
用绳子系一物体,在竖直平面内作圆周运动,当这物体达到最高点时,(1)有人说:“这时物体受到三个力:重力、绳子的拉力以及向心力”;(2)又有人说:“因为这三个力的方向都是向下的,但物体不下落,可见物体还受到一个方向向上的离心力和这些力平衡着”。这两种说法对吗?
用绳子系一物体,在竖直平面内作圆周运动,当这物体达到最高点时,(1)有人说:“这时物体受到三个力:重力、绳子的拉力以及向心力”;(2)又有人说:“因为这三个力的方向都是向下的,但物体不下落,可见物体还受到一个方向向上的离心力和这些力平衡着”。这两种说法对吗?
第1题
A、their home address
B、their favorite picture
C、names of their parents
D、income of themselves
第2题
第3题
第4题
() My mother is retired. My father is a manager.
A. What are your parents doing right now
B. Do your parents still work
C. What do your parents do
第5题
听力原文:M: How often do you go back to visit your parents?
F: Um... usually twice a year.
How often does the woman go home to see her patents?
A.Four times a year.
B.Twice a year.
C.Once a year.
第6题
Your long-term success in event planning will be based()the experience you had.
A. to
B. on
C. of
第7题
A.give my wish to your parents
B.give my best to your parents
C.say good to your parents
D.say greeting to your parents
第8题
- _______ - Well, they got there last Wednesday. So about a week.
A:When did your parents arrive in Paris?
B:How long have your parents been in Paris?
C:Did your parents arrive in Paris last Wednesday?
D:When will your parents go to Paris?
第9题
A.give my wish to your parents
B.give my best to your parents
C.say good to your parents
D.say greeting to your parents
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