Question

Why is the answer A... 0.5E ..?
In attached file.

Answer 1

Because when it reaches that point, Vy=0 and it posses just Vx (which is the same)
\[v_x=v/\sqrt{2}\]
Kinetic energy is 1/2mv2, so
Ef=1/2mVx^2=1/2mV^2/2 , so 1/2E

Answer 2

Aaah okay makes sense all we had to do was use the kinetic energy formula?
And is Vy is always =0 when air resistance is negligible?
So they stated 45\[45^{o}\] just to confuse ?

Answer 3

Nope, 45° is important to determine what is Vx. in fact Vx= Vcos45.
Vy in the highest point is always zero, regardless from air drag :)

Answer 4

Thank you so much (: @Armi