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How do you calculate gravitational potential force?

Published in Physics - Gravity 3 mins read

The question should be 'How do you calculate gravitational force?' Gravitational potential energy is related but different. To calculate gravitational force between two objects, you use Newton's Law of Universal Gravitation.

Here's a breakdown:

Newton's Law of Universal Gravitation

Newton's Law of Universal Gravitation states that every particle attracts every other particle in the universe with a force that is:

  • Proportional to the product of their masses
  • Inversely proportional to the square of the distance between their centers

The Formula

The formula for calculating the gravitational force (F) is:

F = G * (m1 * m2) / r²

Where:

  • F is the gravitational force between the two objects (measured in Newtons, N).
  • G is the gravitational constant, approximately 6.674 × 10⁻¹¹ N⋅m²/kg².
  • m1 is the mass of the first object (measured in kilograms, kg).
  • m2 is the mass of the second object (measured in kilograms, kg).
  • r is the distance between the centers of the two objects (measured in meters, m).

Steps to Calculate Gravitational Force

  1. Identify the masses (m1 and m2) of the two objects. Make sure they are in kilograms (kg).
  2. Determine the distance (r) between the centers of the two objects. Ensure it's in meters (m).
  3. Plug the values of m1, m2, r, and G into the formula.
  4. Calculate the gravitational force (F). The result will be in Newtons (N).

Example

Let's say we want to calculate the gravitational force between the Earth and a 1 kg object on its surface.

  • Mass of Earth (m1) ≈ 5.972 × 10²⁴ kg
  • Mass of the object (m2) = 1 kg
  • Radius of Earth (r) ≈ 6.371 × 10⁶ m
  • Gravitational constant (G) ≈ 6.674 × 10⁻¹¹ N⋅m²/kg²
F = (6.674 × 10⁻¹¹ N⋅m²/kg²) * (5.972 × 10²⁴ kg * 1 kg) / (6.371 × 10⁶ m)²
F ≈ 9.8 N

This result shows that the gravitational force acting on the 1 kg object is approximately 9.8 N, which corresponds to the weight of the object due to Earth's gravity.

Gravitational Potential Energy (Related Concept)

While the original question asked about force, the provided reference mentions gravitational potential energy. It's important to differentiate.

Gravitational potential energy (GPE) is the energy an object possesses because of its position in a gravitational field. The formula for GPE near the Earth's surface is:

GPE = mgh

Where:

  • GPE is the gravitational potential energy (measured in Joules, J).
  • m is the mass of the object (in kg).
  • g is the acceleration due to gravity (approximately 9.8 m/s² on Earth).
  • h is the height of the object above a reference point (in meters).

Gravitational force is the attractive force between objects with mass, while gravitational potential energy is the energy an object has due to its position in a gravitational field. They are related, as the work done by gravity is related to the change in gravitational potential energy.