A bullet of mass 200 g having initial kinetic energy 90 J is shot inside a long swimming pool as shown in the figure. If it's kinetic energy reduces to 40 J within 1 s , the minimum length of the pool, the bullet has to travel so that it completely comes to rest is

Step-by-step solution

Let us assume that the motion of the bullet is of constant retardation inside the water. Initial kinetic energy 1 2 m v 0 2 = 90   J ⇒ v 0 = 30   m   s - 1 Let the retardation is a , then after 1   s 1 2 m 30 - a × 1 2 = 40   J ⇒ 30 - a = 20 ⇒ a = 10   m   s - 2 Stopping distance for the constant retardation is given by, l = u 2 2 a = 30 2 20 = 45   m . Therefore, the minimum length of the pool required is 45   m .