Prove that the magnitude of the ratio of the difference in speeds after collision, to the difference in speeds before collision, for a one-dimensional elastic collision,equal to one.
Answers
Answer:
Solution :
To show relative velocity of approach of two colliding bodies before collision is equal to relative velocity of separation after collision .
Let two bodies of masses m1,m2 are moving with velocities u1,u2 along the straight line in same direction collided elastically .
Let their velocities after collision be v1andv2 .
According to the law of conservation of linear momentum
m1u1+m2u2=m1v1+m2v2
m1(u1−v1)=m2(v2−u2) ....(1)
According to law of conservation of kinetic energy
12m1u21+12m2u22=12m1v21+12m2v22
m1(u21−v21)=m2(v22−u22) ...(2)
Dividing eqn . (2) by (1)
u21−v21u1−v1=v22−u22v2−u2 (or)
u1+v1=v2+u2⇒u1−u2=v2−v1....(3)
i.e, relative velocity of approach of the two bodies before collision = relative velocity of separation of the two bodies after collision . So coefficient of restitution is equal to 'l'.