- #1
ZxcvbnM2000
- 64
- 1
Hello everyone , here we go :
I understand that momentum is always conserved as long as no external forces act on a given system . I also understand that the law of restitution applies to the axis perpendicular to the line of impact between two objects .However i have a problem .
For example . A ball hits the ground at an angle of 45 degrees and bounces up at an angle of 30 degrees.
So from the law of restitution : e= - ( Vball*sin30 - Vground)/(Uball*sin45 - U ground) , the ground does not move therefore Uground = Vground=0 so
e = - Vball*sin30/(Uball*sin45).
My question is , why can't we apply momentum conservation on the y-axis ? Is it because the reaction force when hitting the ground is considered an external force ?
I am very confused please explain :S
Thank you !
I understand that momentum is always conserved as long as no external forces act on a given system . I also understand that the law of restitution applies to the axis perpendicular to the line of impact between two objects .However i have a problem .
For example . A ball hits the ground at an angle of 45 degrees and bounces up at an angle of 30 degrees.
So from the law of restitution : e= - ( Vball*sin30 - Vground)/(Uball*sin45 - U ground) , the ground does not move therefore Uground = Vground=0 so
e = - Vball*sin30/(Uball*sin45).
My question is , why can't we apply momentum conservation on the y-axis ? Is it because the reaction force when hitting the ground is considered an external force ?
I am very confused please explain :S
Thank you !