Hall storms are observed to strike the surface of the frozen lake at 300  with the vertical and rebound at 600  with the vertical. Assume contact to be smooth, the coefficient of restitution is:

Components of velocity before and after collision parallel to the plane are equal, sovsin600=usin300                ……….(i)Components of velocity normal to the plane are related to each other         vcos600=eu(cos300)         ……….(ii)⇒cot600=ecot300⇒e=cot600cot300⇒e=133⇒e=13