Question

A ball whose kinetic energy is `E` , is projected at an angle of `45(@)` to the horizontal . The kinetic energy of the ball at the highest point of its flight will be
A. `E`
B. `(E)/sqrt(2)`
C. `(E)/(2)`
D. `zero`

Answer 1

Correct Answer - C
Let `u` be the speed with which the ball of mass `m` is projected . Then the kinetic energy `(E)` at the point of projection is
` E = 1/2 mu^(2)`
When the ball is at the highest point of its flight, the speed of the ball is `(u)/(sqrt(2))` (Remember that the horizontal component of velocity does not change during a projectile motion).
`:.` The kinetic energy at the hightest point
` = 1/2 m (( u)/sqrt2)^(2) = 1/2 (m u^(2))/2 = E/2` [ from (i)]