When an object is thrown straight up into the air, its acceleration is always downward, even when it's moving upward.

Here's why:

* Gravity: The only force acting on the object after it's released is gravity. Gravity pulls everything towards the center of the Earth, which means it always acts in the downward direction.

* Acceleration due to gravity: The acceleration caused by gravity is approximately 9.8 m/s² near the Earth's surface. This means that the object's velocity decreases by 9.8 meters per second every second it travels upward.

Important Note: While the object is moving upward, its velocity is decreasing because the acceleration due to gravity is acting against its upward motion.