as a ball moves upwards in the air, by how much does its speed decrease each second?

To determine by how much the speed of a ball decreases each second as it moves upward in the air, we can consider the effects of gravity.

When an object is thrown upward, gravity acts against its motion, causing it to slow down. The amount by which the speed decreases each second is the acceleration due to gravity.

On the surface of the Earth, the acceleration due to gravity is approximately 9.8 meters per second squared (m/s²). This means that the speed of the ball decreases by 9.8 m/s for each second of its upward motion.

Keep in mind that this value assumes no other external factors are affecting the ball's motion, such as air resistance. In reality, other factors may slightly affect the rate of speed decrease.