Question

A ball is projected with kinetic energy $E$ at an angle $\theta$ with the horizontal. At the highest point of parabola, the kinetic energy becomes:

• A. $E\cos \theta$
• B. $E{\cos }^2\theta$
• C. $E\sin \theta$
• D. $E{\sin }^2\theta$

Answer 1

The correct option is B $E{\cos }^2\theta$

Option B is correct
$K.E=E=\frac{1}{2}m{v}^2$
At highest point, $v_x=v\cos \theta$ and $v_y=0$
So, kinetic energy at the highest point $K{E}_h=\frac{1}{2}m(v_x^2+v_y^2)=\frac{1}{2}m{v}^{2}co{s}^2\theta$
$⟹K{E}_h=E{\cos }^2\theta$