1. The problem statement, all variables and given/known data A stone is thrown keeping target to a mango hanging in the branch of a mango tree. The velocity of the stone while hitting the mango is 9.8ms^-1. If the boy uses half of the energy used before the stone can reach the same height of the mango. Mass of the mango is 250gm. 2. Relevant equations v^2=u^2-2gh 3. The attempt at a solution According to the question the final velocity of the stone hitting the mango should be 9.8ms^-1. The velocity with which the boy projected the stone vertically should be greater than 9.8ms^-1 since it should be enough to counteract the gravitational acceleration. So we can say that the kinetic energy the the stone gains is half the kinetic energy the boy uses to project the stone. The workout is shown below and if I make any silly mistakes or misinterpret the question please point out my mistake and please see if the answer I got is reasonable enough Let the velocity with which the boy projects the stone be v1 final velocity of the stone v2=9.8ms^-1 According to first condition Ek1/2=Ek2 v1^2/2= v^2 v1= √2 v2 Hence, v1= 13.86ms^-1≈ v2^2=v1^2-2gh or, (9.8)^2= (13.86)^2-19.6h or, 96.04-192.1= -19.6h or, h= 96.06/19.6 h= 4.9meters Sorry, I don't have the answer to this prob in my book so I have to make sure if this is the correct one..