A uncleus is at rest in the laboratory frame of reference . Show that if it disintegrtes into two smaller unclel the products must move in opposite directions .

Explanation

Let `m_(1),m_(2)` be the masses of products and `vec(v_(1)),vec(v_(2))` be their repective velocities Therfore, total linear momentum after disinte-gration = `m_(1)vec(v_(1))+m_(2)vec(v_(2))` . Before disintegration , the uncleus is at rest . Therefore , its linear momentum before disintegration is zero .
According to the principle of conservation of linera momentum ,
`m_(1)vec(v_(1))+m_(2)vec(v_(2))=0" or " vec(v_(2))=(-m_(1)vec(v_(1)))/(m_(2))`
Negative sign shows that `vec(v_(1))and vec(v_(2))` are in opposite directions .