Short Answer 
The vertical acceleration due to gravity is a constant -9.8 m/s², affecting all objects in free fall equally, regardless of their mass. This acceleration remains consistent over time, as demonstrated by a velocity-time graph showing a straight line with a negative slope of -9.8 m/s², indicating that it does not change throughout the fall.
Step 1: Understand the Concept of Vertical Acceleration
The vertical component of acceleration due to gravity is a constant value of -9.8 m/s². This indicates that all objects in free fall experience the same acceleration towards the Earth, regardless of their mass or shape. This consistent downward acceleration is a fundamental principle of physics.
Step 2: Acknowledge the Consistency Over Time
At any point in time during free fall, including at tm = 325s, the vertical acceleration remains -9.8 m/s². This is because the influence of gravity does not change, leading to a constant vertical acceleration. The equation can be simplified as:
- Acceleration = -g
- g = 9.8 m/s²
Step 3: Visualize with a Velocity-Time Graph
The relationship between velocity and time can be visualized using a velocity-time graph, also known as a v vs. t graph. In this graph, the slope represents acceleration. Given that the vertical acceleration due to gravity is constant, the graph will display:
- A straight line
- A negative gradient (slope) equal to -9.8 m/s²