Free fall: a ball is thrown straight up. why is the acceleration not zero, but k

Question

Free fall: a ball is thrown straight up. why is the acceleration not zero, but kinetic energy zero? Shouldn't there be no velocity at the top?
Note: velocity should equal zero because it stopped moving, therefore there should be no acceleration because there is no velocity? Right?! 3. a. (i pt.) A baseball is thrown straight up. (gnore air resistance.) Taking the +y-direction to be upward, which one of the following is TRUE about the ball at the top of its arc? A. Its velocity is -9.8 m/s. B. Its acceleration is zero. Its weight is zero. D Its kinetic energy is zero.

Explanation / Answer

along vertical

initial velocity = voy

acceleration ay = -g = -9.8 m/s^2

displacement = +ve

weight W = mg

at the highest point the ball is instantaneously at rest

so the velocity is zero at top vy = 0

kinetic energy K = (1/2)*m*vy^2 = 0 <<--answer

D is TRUE

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