Overview
This lecture explains the difference between contact and non-contact forces, provides examples of each, and covers key definitions important for understanding forces in physics.
What is a Force?
- A force is a push or pull acting on an object due to interaction with another object.
- All forces have both magnitude (size) and direction, making them vector quantities.
- The unit of force is the Newton (N).
Contact Forces
- Contact forces occur when two objects are physically touching.
- Tension in a rope is a contact force, such as when pulling in a tug of war.
- Friction is a contact force acting between surfaces, e.g., an airplane slowing down on water.
- Air resistance is a contact force caused by air particles colliding with an object, e.g., a skydiver’s parachute.
- Normal contact force is the upward force exerted by a surface supporting an object, only present when objects are in direct contact.
Non-Contact Forces
- Non-contact forces act between objects that are physically separated.
- Gravitational force attracts any two objects, such as the Earth and the International Space Station.
- Electrostatic force occurs between charged objects; opposite charges attract and like charges repel.
- Magnetic force is experienced by certain objects in a magnetic field.
Key Terms & Definitions
- Force — a push or pull acting on an object due to interaction with another object.
- Vector quantity — a quantity with both magnitude and direction.
- Contact force — force between objects that are physically touching.
- Non-contact force — force between objects that are physically separated.
- Tension — force transmitted through a stretched object like a rope.
- Friction — force resisting motion between surfaces in contact.
- Air resistance — force opposing motion of objects through air.
- Normal contact force — upward force exerted by a surface on an object resting on it.
- Gravitational force — attractive force between masses.
- Electrostatic force — force between electrically charged objects.
- Magnetic force — force experienced in a magnetic field.
Action Items / Next Steps
- Review questions on contact and non-contact forces in the revision workbook.
- Prepare for further study of weight and magnetic forces in upcoming videos.