Physics简单问题

发布网友发布时间：2023-05-19 04:32

共1个回答

热心网友时间：2024-06-01 05:10

更新1:

加上解释唔该晒~

This question is a tricky one. The correct statement is B. Throughout the process
the weight of the rock always acts in the down direction
even when it is at the top of its path. So
statement D is wrong. The tricky part is as follows: If air resistance is not taken into account
then the force acting on the rock is its weight
pointing downward throughout the process. If air resistance is taken into account
then the air resistance will oppose the direction of motion of the rock. That is it acts downward when the rock is moving upward
and vice versa. The force acting on the rock is always downward since it is always accelerating downward. Note that air resistance is proportional to its speed. So
when the rock is at its top position of its path
it is instantaneously at rest and hence the air resistance acting on it is zero. And the force acting on the rock is only its weight. So
statement C
D and E are wrong.
参考: Physics king