Gravitational Potential Questions | A Level Physics | Formulas, Key Words, Graphs

This paragraph introduces the concept of gravitational potential, distinguishing it from gravitational field strength and force. Gravitational potential is related to the energy an object has due to gravity. The definition provided is the work done to bring a unit mass from infinity to a specific point. The script also explains that at an infinite distance from any mass, the force is zero, and thus the potential is considered zero. The video aims to clarify this concept and its relation to energy.

The second paragraph deals with a physics problem involving a satellite of mass 360 kg orbiting the Earth. The problem requires calculating the radius of the satellite's orbit using the given period of orbit and the mass of the Earth. The solution involves converting the period into seconds and equating the centripetal force (required for circular motion) to the gravitational force. After rearranging the formula and substituting the given values, the radius of the orbit is found to be 2.4 x 10^8 meters.

This part of the script focuses on calculating the change in gravitational potential energy as a satellite moves from its orbit to a position on the Earth's surface. The formula for gravitational potential, Phi = -GM/r, is introduced, where G is the gravitational constant, M is the mass of the Earth, and r is the distance from the center of the Earth. The change in potential energy (Delta E) is calculated by finding the difference in potential at the satellite's orbit and on the Earth's surface, resulting in 2.2 x 10^10 joules.

The fourth paragraph explains the relationship between gravitational potential and gravitational field strength. It states that the field strength is the gradient of the potential, which can be found by dividing the potential by the distance (R). The script also discusses a scenario involving a moon and a planet, using a graph to illustrate the gravitational potential at various points between them. It is explained that the potential is negative throughout the range because gravitational force is attractive, causing potential energy to decrease as mass approaches from infinity.

The final paragraph delves into analyzing gravitational potential graphs, particularly focusing on the characteristics of the graph provided. It describes features such as the negative potential throughout the graph, the maximum potential being closer to the moon than the planet due to the steeper potential gradient of the more massive Earth, and the inverse proportionality of potential to distance from the planet or moon. The paragraph concludes with an exercise to sketch the variation of gravitational field strength at a point between the planet and the moon, noting that the field strength will hit zero at a certain point as the opposing forces balance each other out.