DON T confuse accel and velocity!
{"Image DocumentName": "DON T confuse accel and velocity!", "Image ImageDescription": "What is the magnitude and direction (if any) of the acceleration of the ball at the instant it reaches the highest point in its trajectory? What is its acceleration just before it hits the ground upon its return journey? (Correct: 18 Wrong:13 No Ans: 16)\u200f At the peak of the trajectory flight, the ball has no magnitude or direction, for that instant; however it then immediately accelerates downwards at 9.8 m/s2. I don t know the streets names, but I guess, the magnitude of the acceleration of the ball at the highest point in trajectory, it will be 9.81m/s^2(same as gravitational force) and the direction is upward or no direction,because the direction was headed to upward during the time it goes up,but at the top,because it stops for a moment, maybe there s no direction. The magnitude of the acceleration of the ball the instant it reaches the highest point in its trajectory is 9.8 m/s2. The acceleration just before the ball hits the floor is 0 m/s2. DON T confuse accel and velocity! The direction is DOWN (not just negative , the sign means nothing if you don t specify the coordinate system!).", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}