A body of mass 1 ~kg is thrown upwards with a velocity 20 ~ms ⁻¹ . It momentarily comes to rest after attaining a height of 18 ~m . How much energy is lost due to air friction ? ( g =10 ~ms ⁻² )

Step-by-step solution

Key Idea The energy lost due to air friction is equal to difference of initial kinetic energy and final potential energy. Initially body posses only kinetic energy and after attaining a height the kinetic energy is zero. Therefore, loss of energy = KE - PE aligned & = 1 2 mv ^2- mgh & = 1 2 1 400-1 18 10 & =200-180=20 ~J aligned