✔ 最佳答案
Basically, there are three kinds of collision.
1. elastic collision
the total kinetic energy of collided objects conserves
2.inelastic collision
the total kinetic energy of collided objects decreases
3.explosion
the total kinetic energy of collided objects increases
However, the total monentum of the collided objects are conserved (unchange) unless there are external forces applied.
When doing calculcation about monentum, you should find out the velocity and mass of the object before or after the collisions respectively.
the general equaion:total mv before collision=total mv after collision
例如, 車a(1000kg, 30m/s) 撞車b(1500kg, at rest) 佢地stick together
搵佢地撞後既速度
1000x30+0x1500=(1000+1500)v
但若果車a 反彈(10m/s)
要搵車b既速度
咁就
1000x30+0x1500=1000x-10+1500v
若果車b係迎頭撞(10m/s) 咁就
1000x30+ -10x1500=1000x-10+1500v
velocity係有方向的
