Question

pls give me answers of this and

Answer 1

1. when two bodies colloid with each other linear momentum of the bodies. 
 initial momentum = m1v1 
initial momentum of 2 nd body=m2v2 
final m=m1v1 
final m 2nd body=m2v2 
compined=m1v1+m2v2
f1=m1v1-m2v2/t 
f2=m2v2-m2v2/t
m1v1-m2v2/t
m2v2-m2v2/t
m1v1+m2v2=m1v1=m2v2