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Free fall is a type of motion in which an object is only influenced by gravity. When an object is in free fall, it experiences acceleration due to gravity, with other forces such as air resistance being negligible. This means that any object freely falling under the influence of gravity will have a uniform acceleration towards the Earth.

In our example of the brick being dropped from a building, it starts from rest, with no initial velocity. Thus, it is purely under the effect of gravitational pull. The constant acceleration of the brick constitutes what we commonly refer to as free fall. It's noteworthy that free fall doesn't necessarily imply a lack of velocity—just that the only force acting on the object is gravity.

Remember, every object regardless of its mass accelerates at the same rate when in free fall. Therefore, both a feather and a brick would, theoretically in a vacuum, fall at the same time from the same height.

In the context of kinematics, the acceleration due to gravity is denoted by the symbol \( g \). On Earth, this value is approximately \( 9.81 \, \text{m/s}^2 \). This means that for every second an object is in free fall, its velocity increases by \( 9.81 \, \text{m/s} \), assuming air resistance is negligible.

When solving physics problems involving objects in free fall, such as the dropping brick from the building, it is essential to apply \( g \) as the acceleration. In these calculations, knowing \( g \) allows us to compute both the distance the object travels and its speed at a given time while falling.

Since \( g \) is consistent, it provides a reliable basis for predictions and calculations in any free-fall scenario. The magnitude remains constant at \( 9.81 \, \text{m/s}^2 \), no matter how high the object starts from.

Kinematic equations are crucial in solving problems related to motion, especially in free fall. They simplify the calculation of variables such as distance, time, and velocity. In the scenario involving the brick, the following kinematic equations are applied:

• To find the height of the building, we use:
  \[ y = v_i t + \frac{1}{2} a t^2 \]
  where \( y \) is the displacement, and \( a \) is the acceleration.


• To find the final velocity just before impact, we apply:
  \[ v_f = v_i + at \]
  where \( v_f \) is the final velocity.
  

These equations involve basic parameters: initial velocity \( v_i \), final velocity \( v_f \), acceleration \( a \), time \( t \), and displacement \( y \). Each problem requires substituting known values to solve for unknown variables. Mastery in using kinematic formulas allows anyone to analyze and predict the motion of freely falling objects effectively.

A velocity-time graph is a powerful tool for visualizing an object's motion over time. In such a graph, velocity is plotted on the vertical axis, while time is on the horizontal axis. For a brick in free fall, the velocity-time graph presents as a straight line:

• The graph starts at the origin point, indicating the initial velocity \( v_i \) is zero.


• It has a positive slope of \( 9.81 \, \text{m/s}^2 \), corresponding to the constant acceleration due to gravity.


• The line extends up to \( v_f = 24.53 \, \text{m/s} \) at \( t = 2.50 \, \text{s} \).

The consistent slope reflects the unchanging acceleration. You can determine the velocity at any point during the fall by simply looking at the graph. The more time passes, the higher the velocity increases, linearly.

This representation helps to better understand how acceleration maintains its role in increasing velocity over time during free fall.