What is the Horizontal acceleration of an object thrown into the air?
When you throw an object into the air it experiences only downward acceleration due to gravity. You say use a magnitude10m/s² which is the acceleration downwards. There is no net force acting on the body horizontally, so the horizontal acceleration is zero. When we do projectile problems, and ignore air resistance as you agree, we always take the horizontal velocity component as constant, meaning no acceleration.
