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An object's motion is separated into two unique and independent components. Because the pull of gravity is a constant uniform acceleration of 9.8m/s^2, down, any object that is in free-fall will hit the ground at the same time as an object thrown horizontally. Any horizontal velocity will not have an effect on the vertical motion.
Gravity:: Excluding air resistance, at any given location on earth, gravity affects all objects in the same way, with the same constant uniform acceleration. Therefore, two objects of differing weights, sizes, and shapes that are dropped from the same height, will land on the ground simultaneously.
Santa's Fun with Objects in Motion
The instant an object leaves a surface like a table, the normal force countering gravity disappears, and it starts to fall at an increasing rate due to gravity. Therefore, the vertical velocity (Vy) is constantly changing. The horizontal
velocity (Vx) remains constant during the trajectory because gravity is the only force acting upon the object in the air so Vx = Vox. The resultant velocity at each point on the path is found with the equation Vo = square root (Vox^2 + Voy^2).
When objects are pointed at an angle, the motion is
practically constant horizontal velocity combined with vertical motion such as throwing a ball straight up. Because of the downward acceleration of gravity, Vy will continually decrease until it reaches the top of its path when Vy = 0 m/s. Then the velocity will start to increase in the negative direction as the object starts to fall.