Dec 2016

Gravitational Field

December 21, 2016


Physics tuition will definitely help you on what seems like an overwhelming topic, the basic concepts embodied in physics are actually pretty easy to follow. Let us look at one of the core concepts of JC physics – gravitational field- and let us simplify it for you.

What is a Gravitational Field?

The gravitational field is the surrounding field generated by an object with mass and it’s another way of defining Newton’s law of gravity. Should you divide the mass of an object by the force of gravity at any given point, your result will be the gravitational field.

What is the Use of Measuring a Gravitational Field?

The gravitational field is a model used to help us understand how bodies with large mass produce forces on the space around them, particularly on other massive bodies. It’s generally thought of as a field model- it’s not the two particles attracting each other, but rather that their mass distorts space-time and that is what is perceived as the ‘force’ of gravity.

Everything has gravity or in other words, attracts things to itself- including our bodies. We just don’t notice these forces of attraction unless the body has a huge mass of the sun and earth.

What do I need to know about gravitational fields?

  • Interaction of gravitational fields [push and pull exerted by massive bodies] is the reason behind phenomena such as tide and global warming
  • Gravity is attractive- things are pulled towards things
  • This force is a vector- it has direction and value
  • Point masses are used in gravity calculation- assuming all the mass is at the center of the object for simplicity’s sake
  • Gravity calculations are done with Newton’s Universal Law

What is Newton’s Universal Law?

Mostly this is expressed as the following:

F = (-) GMm/r^2

M would be the large mass, m the smaller, G the gravitational constant [6.67×10^-11 Nm^2kg^-2] and r the distance between the centers of the two objects when measured in meters.

Is This an Inverse Square Law?

Yes, it is! Like many concepts in physics, this is an inverse square law- force decreases with the square of the separation.

What is Gravitational Potential Energy?

Gravitational Potential Energy [GPE] is the work needed to move the smaller object a certain distance from the larger. Gravitational potential energy would be zero at an infinite distance from the mass. In reality, what this means is the GPE fluctuates as the little object gets closer to or further from the big object. The relevant formula is:

GPE= – GMm/r

This concept goes hand in hand with gravitational potential, which is that GPE per unit of mass.

GP = -GM/r

These two concepts are important for understanding how gravity acts on a mass. Using this concept you can work out areas of ‘equipotential’- or areas where the gravitational forces are the same. If you imagine moving along the line plotted between areas that have equipotential, you will not gain or lose energy.

The gravitational field is a vital concept in physics. Without the insight into the workings of gravity, the moon landings, and other vital physics research would never have occurred! If you have any interest in the physics, it’s vital you come to grips with this important concept.

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