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 (g) is not constant everywhere on the surface of the Earth. It varies due to several factors, including latitude, altitude, and the local geological structure of a region. These variations can have a significant impact on the value of g experienced at different locations.
Latitude plays a role in the variation of g because 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 difference in distance affects the gravitational force experienced at these locations, leading to a variation in g. At the poles, where the distance to the center is shorter, the value of g is slightly higher than at the equator.
Altitude also influences the value of g. As one moves higher above the Earth’s surface, the distance to the center of the Earth increases, resulting in a weaker gravitational force and a lower value of g. This decrease in g with altitude is due to the inverse square law of gravity, which states that the force of gravity decreases with the square of the distance between two objects.
Additionally, the local geological structure of a region can cause variations in g. Variations in the density and distribution of rocks and minerals beneath the Earth’s surface can affect the gravitational field in that area. For example, regions with denser materials, such as mountains or deep ocean trenches, will experience a slightly higher value of g compared to regions with less dense materials, like sedimentary plains.
Understanding how location affects the value of g is essential in various scientific fields. For instance, in geophysics and geodesy, precise measurements of g are crucial for studying the Earth’s structure and determining accurate geodetic reference systems. In engineering, knowledge of g variations is necessary for designing structures and calculating forces acting on them. Furthermore, in space exploration, understanding variations in g is vital for planning spacecraft trajectories and conducting experiments in microgravity environments.
By using the Gravitational Fields widget, you can explore how changes in latitude, altitude, and geological structure affect the value of g at different locations on Earth. This tool allows you to gain a deeper understanding of the complex nature of gravity and its impact on our planet.
The value of g, which represents the acceleration due to gravity, is influenced by various factors such as location, latitude, altitude, and geological structure. Understanding these influences is crucial in several scientific fields.
In geophysics and geodesy, precise measurements of g are essential for studying the Earth’s structure and determining accurate geodetic reference systems. By analyzing variations in g at different locations, scientists can gain insights into the distribution of mass within the Earth, including the density and composition of its various layers. This information is vital for understanding processes such as plate tectonics, mantle convection, and the formation of geological features.
In engineering, knowledge of g variations is necessary for designing structures and calculating the forces acting on them. The acceleration due to gravity affects the stability and load-bearing capacity of buildings, bridges, and other infrastructure. By considering variations in g, engineers can ensure the safety and integrity of structures in different locations. For example, in areas with lower values of g, such as at high altitudes or near the equator, the design of structures may need to account for reduced gravitational forces.
In space exploration, understanding variations in g is vital for planning spacecraft trajectories and conducting experiments in microgravity environments. The gravitational field of Earth is not uniform, and variations in g can affect the trajectory and orbital dynamics of spacecraft. By accurately measuring and modeling these variations, scientists and engineers can optimize spacecraft trajectories, reducing fuel consumption and mission duration. Additionally, in experiments conducted in microgravity environments, where g is significantly reduced, scientists can study the behavior of materials and biological systems under conditions not experienced on Earth.
The Gravitational Fields widget provides a valuable tool for exploring how changes in latitude, altitude, and geological structure affect the value of g at different locations on Earth. By inputting specific parameters, users can visualize and analyze the complex nature of gravity’s influence on our planet. This tool enhances our understanding of how gravity varies across the Earth’s surface, enabling researchers and professionals in various fields to make more informed decisions and calculations based on location-specific gravitational forces.