F.4 Physics 一個關於inertia既問題 測驗用
If plane A has mass:150000kg Plane B has mass:200000 kg.
A and B travel at constant velocities of 600 km/h and 150km/h.
Then , A and B have the same inertia and the same net force acting on them?
if i press a toy on a table(由上向下),is there any friction?
- 天同Lv 77 年前最愛解答
Inertia is described by Newton's First Law of Motion. It states that any body tends to remain at its state of rest or uniform motion in a straight line unless it is acted upon by an external force.
(a) When the train speeds up, you tends to remain at your original position relative to the station because of inertia. Hence, you feel that you are being thrown backward.
(b) When the train moves at constant speed, you need no force to keep you moving. As such, you feel no force acting on you.
(c) When the train stops, because of inertia, you tends to continue travelling forward. Hence, you feel that you are being thrown forward.
"Mass" is a physical quantity used to measure inertia. The larger the mass of an object, the more difficult to change its state of rest or motion, hence the larger the inertia is.
Since plane B has a mass larger than plane A, plane B has got a larger inertia than plane A does. That is to say, it is more difficult to change the state of motion (like the speed, direction, altitude etc) of plane B than that of plane A.
Any object moving at constant speed is under no net force, because it moves by its own inertia. Therefore, the net forces acting on both plane A and plane B are zero.
2013-10-27 17:34:51 補充：
Q: if i press a toy on a table(由上向下),is there any friction?
A: No, you only increase the normal reaction on the toy.