A free falling object is an object that is falling under the sole influence of gravity. Any object that is being acted upon only by the force of gravity is said to be in a state of free fall. There are two important motion characteristics that are true of free-falling objects:
Because free-falling objects are accelerating downwards at a rate of 9.8 m/s/s, a ticker tape trace or dot diagram of its motion would depict an acceleration. The dot diagram at the right depicts the acceleration of a free-falling object. The position of the object at regular time intervals – say, every 0.1 second – is shown. The fact that the distance that the object travels every interval of time is increasing is a sure sign that the ball is speeding up as it falls downward. Recall from an earlier lesson, that if an object travels downward and speeds up, then its acceleration is downward.
Free-fall acceleration is often witnessed in a physics classroom by means of an ever-popular strobe light demonstration. The room is darkened and a jug full of water is connected by a tube to a medicine dropper. The dropper drips water and the strobe illuminates the falling droplets at a regular rate – say once every 0.2 seconds. Instead of seeing a stream of water free-falling from the medicine dropper, several consecutive drops with increasing separation distance are seen. The pattern of drops resembles the dot diagram shown in the graphic at the right.
It was learned in the previous part of this lesson that a free-falling object is an object that is falling under the sole influence of gravity. A free-falling object has an acceleration of 9.8 m/s/s, downward (on Earth). This numerical value for the acceleration of a free-falling object is such an important value that it is given a special name. It is known as the acceleration of gravity – the acceleration for any object moving under the sole influence of gravity. A matter of fact, this quantity known as the acceleration of gravity is such an important quantity that physicists have a special symbol to denote it – the symbol g. The numerical value for the acceleration of gravity is most accurately known as 9.8 m/s/s. There are slight variations in this numerical value (to the second decimal place) that are dependent primarily upon on altitude. We will occasionally use the approximated value of 10 m/s/s in The Physics Classroom Tutorial in order to reduce the complexity of the many mathematical tasks that we will perform with this number. By so doing, we will be able to better focus on the conceptual nature of physics without too much of a sacrifice in numerical accuracy.
The value of the acceleration of gravity (g) is different in different gravitational environments. Use the Value of g widget below to look up the acceleration of gravity on other planets. Select a location from the pull-down menu; then click the Submit button.
Even on the surface of the Earth, there are local variations in the value of the acceleration of gravity (g). These variations are due to latitude, altitude and the local geological structure of the region. Use the Gravitational Fields widget below to investigate how location affects the value of g.
Recall from an earlier lesson that acceleration is the rate at which an object changes its velocity. It is the ratio of velocity change to time between any two points in an objects path. To accelerate at 9.8 m/s/s means to change the velocity by 9.8 m/s each second.
The acceleration of gravity, denoted as "g," is a fundamental concept in physics that describes the rate at which an object falls due to the force of gravity. However, it is important to note that the value of g is not constant across the entire surface of the Earth. There are local variations in g that are influenced by several factors, including latitude, altitude, and the local geological structure of a region.
Latitude plays a significant role in the variation of g. The Earth is not a perfect sphere but rather an oblate spheroid, meaning it is slightly flattened at the poles and bulges at the equator. As a result, the distance from the center of the Earth to a point on its surface is shorter at the poles than at the equator. This variation in distance affects the gravitational force experienced at different latitudes, resulting in a slight difference in the value of g.
Altitude is another factor that affects the value of g. As one moves higher above the Earth’s surface, the distance to the center of the Earth increases. Since gravity weakens with distance, the gravitational force experienced at higher altitudes is slightly weaker compared to that at lower altitudes. Consequently, the value of g decreases as altitude increases.
The local geological structure of a region can also influence the value of g. Variations in the density and distribution of rocks and minerals beneath the Earth’s surface can cause local variations in gravitational acceleration. For example, regions with denser rock formations may experience slightly higher values of g compared to regions with less dense formations.
To better understand how location affects the value of g, you can use the Gravitational Fields widget provided below. This interactive tool allows you to explore different locations on Earth and observe how the value of g changes based on latitude, altitude, and geological structure. By investigating these variations, you can gain a deeper appreciation for the complexities of gravity and its impact on our everyday lives.
In summary, the value of the acceleration of gravity, g, is not constant across the surface of the Earth. It varies due to factors such as latitude, altitude, and the local geological structure of a region. Understanding these variations is crucial for various scientific and engineering applications and can be explored using tools like the Gravitational Fields widget.