Question: when a ball is thrown straight up the acceleration at its highest point is?
Answer: At it's highest point, acceleration is zero. Then it begins it accelerates downwards. Upon acceleration, the ball will increase exponentially up to 180 mph. -9.8 m/s/s; the ball must stop before it changes direction to fall back down so the velocity at the apex of the trip is 0 but a is always 9.81 m/s/s at all times.