Gravitational force

Definition

Gravitational force is the attractive force that exists between any two masses, drawing them together. This fundamental force is responsible for a wide range of phenomena, from keeping planets in orbit around stars to the motion of objects on Earth. It plays a key role in understanding motion, equilibrium, and orbits, particularly how bodies interact within gravitational fields.

5 Must Know Facts For Your Next Test

1. Gravitational force is always attractive and acts over infinite distances, though its strength decreases with distance.
2. The acceleration due to gravity on Earth is approximately $$9.81 \, m/s^2$$, which affects all objects regardless of their mass.
3. In dynamic equilibrium, gravitational forces must be balanced by other forces acting on an object, resulting in no net acceleration.
4. When considering curvilinear motion, gravitational force provides the necessary centripetal force to keep an object moving along a curved path.
5. In circular orbits, gravitational force acts as the centripetal force required to maintain the orbiting body's circular path around a larger mass.

Review Questions

• How does gravitational force affect an object in dynamic equilibrium?
  • In dynamic equilibrium, the forces acting on an object are balanced, meaning that the net force is zero. Gravitational force plays a crucial role in this balance by counteracting other forces like tension or friction. For instance, if an object is suspended in mid-air, the gravitational force acting downward is equal to the upward tension from a rope or cable. This balance allows the object to remain at rest or move at a constant velocity without accelerating.
• Explain how gravitational force influences curvilinear motion and provides necessary centripetal force.
  • Gravitational force acts as a centripetal force when an object moves in a curved path under its influence. For example, a satellite orbiting Earth is continuously pulled towards the planet by gravitational force. This pull keeps the satellite moving in its curved trajectory rather than flying off in a straight line. The gravitational attraction ensures that as it moves, it constantly changes direction while maintaining its speed, allowing it to remain in stable orbit.
• Evaluate the implications of gravitational force in both circular and elliptical orbits and how they differ in terms of motion.
  • In circular orbits, gravitational force provides a constant centripetal acceleration that maintains uniform circular motion around a central body. The distance between the orbiting object and the central mass remains constant. In contrast, elliptical orbits involve varying distances between the orbiting body and the central mass, resulting in changes in speed and acceleration due to gravitational force. As per Kepler's laws, the object moves faster when closer to the central mass and slower when further away, showcasing how gravitational pull varies with distance.

Related terms

Newton's Law of Universal Gravitation: A principle stating that every point mass attracts every other point mass in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

Weight: The force exerted by gravity on an object, which is the product of its mass and the acceleration due to gravity at a given location.

Inertia: The resistance of any physical object to any change in its velocity, including changes to the speed or direction of motion.