Types of Forces to Know for College Physics I – Introduction

Forces are all around us, influencing how objects move and interact. Understanding different types of forces, like gravitational, frictional, and tension forces, helps explain everything from falling apples to orbiting planets, making it essential in physics.

1. Gravitational force

   • Attracts two masses towards each other; the strength depends on their masses and the distance between them.
   • Governed by Newton's law of universal gravitation: F = G(m1*m2)/r².
   • Responsible for keeping planets in orbit and objects grounded on Earth.

2. Normal force

   • The force exerted by a surface to support the weight of an object resting on it.
   • Acts perpendicular to the surface; counteracts gravitational force.
   • Changes with the angle of the surface (e.g., inclined planes).

3. Friction force

   • Opposes the relative motion of two surfaces in contact.
   • Depends on the nature of the surfaces and the normal force acting between them.
   • Can be static (preventing motion) or kinetic (during motion).

4. Tension force

   • The pulling force transmitted through a string, rope, or cable when it is pulled tight.
   • Acts along the length of the string and is equal in magnitude at both ends.
   • Commonly encountered in problems involving pulleys and hanging objects.

5. Spring force (elastic force)

   • The force exerted by a compressed or stretched spring, described by Hooke's Law: F = -kx.
   • The force is proportional to the displacement from the equilibrium position.
   • Acts to restore the spring to its original shape.

6. Applied force

   • A force that is applied to an object by a person or another object.
   • Can cause an object to accelerate, decelerate, or change direction.
   • The magnitude and direction can vary depending on the situation.

7. Electrostatic force

   • The force between charged objects, described by Coulomb's law: F = k(q1*q2)/r².
   • Can be attractive or repulsive depending on the nature of the charges (like charges repel, opposite charges attract).
   • Plays a crucial role in atomic and molecular interactions.

8. Magnetic force

   • The force exerted by magnets or moving electric charges, described by the Lorentz force law.
   • Can also be attractive or repulsive, depending on the orientation of the magnetic fields.
   • Essential in the functioning of electric motors and generators.

9. Air resistance (drag force)

   • A type of frictional force that opposes the motion of an object through air.
   • Depends on the object's speed, shape, and surface area.
   • Increases with velocity and can significantly affect the motion of falling objects.

10. Centripetal force

    • The net force required to keep an object moving in a circular path, directed towards the center of the circle.
    • Can be provided by tension, gravity, friction, or other forces depending on the scenario.
    • Essential for understanding the motion of planets, satellites, and objects in circular motion.