First slide
Rectilinear Motion
Question

A body is projected with kinetic energy K at an angle of 60° with the horizontal. Its kinetic energy at the highest point of its trajectory will be

Moderate
Solution

At the highest point, the velocity has only the horizontal component vx=v cosθ=v cos60=v/2.
Now kinetic energy 12mv2 is proportional to v2. Since the velocity is reduced to half, the kinetic energy becomes one-fourth, i.e., K/4. 

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