When we use the scissors to cut an object, which of the following statements is correct?
A The pivot is at the rotation axis in the middle of the scissors.
B The forces applied by the hand form a couple.
C The force applied on the scissors by the hand is always equal to the force applied on the object by the scissors.
D The net torque about the pivot is zero.
The answer is A. Can you tell me why? Can you give me a detailed explanation for each option.
thank you.
S4 Physics force (5m)
2010-06-09 3:12 am
回答 (2)
2010-06-09 3:25 am
✔ 最佳答案
pivot解支點rotation axis 解旋轉對稱
咁個支點一定係個把交剪中間啦
咁係中間 咁姐係有旋轉對稱囉
你當提交剪係一個X 咁個想交點 一定係旋轉對稱啦 e個order 係2
2010-06-08 19:27:39 補充：
B 我諗係無couple 都無兩個力
C moment係F xd 如果個object同支點鉅離 和 力點 與支點鉅離 5同 f都唔同啦
2010-06-08 19:29:02 補充：
D 我諗同c一樣 個DISTANCE 唔一樣 所以未必係0
參考: 自己
2010-06-09 4:32 am
A. The pivot is the point where the two "arms" of the scissors joint together, it is usually located at the middle.
B. No. A couple is a pair of forces of equal magnitude but act on opposite sides of the pivot. Clearly, the forces applied by the hand are all acting on thye same side of the pivot.
C. No. The distance from the pivot to the hand and the distance from the pivot to the object in a pair of scissors are not the same. But the moment given by the hand and the moment given by the object are equal, thus the forces are not equal.
D. Clearly no. If it is zero, you won't be able to use a pair of scissors to cut an object.
B. No. A couple is a pair of forces of equal magnitude but act on opposite sides of the pivot. Clearly, the forces applied by the hand are all acting on thye same side of the pivot.
C. No. The distance from the pivot to the hand and the distance from the pivot to the object in a pair of scissors are not the same. But the moment given by the hand and the moment given by the object are equal, thus the forces are not equal.
D. Clearly no. If it is zero, you won't be able to use a pair of scissors to cut an object.
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