Gravity Fundamentals

Gravity

• Definition: Gravity is a force that attracts two objects with mass towards each other.
• Universal force: Gravity is a universal force that affects everything with mass, from the smallest atoms to the largest galaxies.
• Strength: The strength of gravity depends on the mass of the objects and the distance between them.
• Gravity on Earth: On Earth, gravity pulls objects towards the center of the planet, which is why objects fall towards the ground.
• Weight: Weight is the force exerted on an object by gravity, and it is measured in Newtons (N).

Friction

• Definition: Friction is a force that opposes motion between two surfaces in contact.
• Types of friction:
  • Static friction: The force that prevents an object from moving when a force is applied to it.
  • Kinetic friction: The force that opposes motion when an object is already moving.
  • Rolling friction: The force that opposes motion when an object is rolling on a surface.
  • Fluid friction: The force that opposes motion when an object is moving through a fluid (such as air or water).
• Factors affecting friction:
  • Surface roughness: The rougher the surfaces, the greater the friction.
  • Normal force: The greater the normal force (force perpendicular to the surface), the greater the friction.
  • Surface area: The greater the surface area in contact, the greater the friction.
• Reducing friction: Friction can be reduced by:
  • Using lubricants (such as oil or grease)
  • Polishing surfaces to reduce roughness
  • Reducing the normal force (e.g. by using a ramp instead of a lift)

Gravity

• Gravity is a force that attracts two objects with mass towards each other, making it a universal force that affects everything with mass.
• The strength of gravity depends on the mass of the objects and the distance between them.
• On Earth, gravity pulls objects towards the center of the planet, causing objects to fall towards the ground.
• Weight is the force exerted on an object by gravity, and it is measured in Newtons (N).

Friction

• Friction is a force that opposes motion between two surfaces in contact, and it has several types.
• Static friction is the force that prevents an object from moving when a force is applied to it.
• Kinetic friction is the force that opposes motion when an object is already moving.
• Rolling friction is the force that opposes motion when an object is rolling on a surface.
• Fluid friction is the force that opposes motion when an object is moving through a fluid (such as air or water).
• Factors that affect friction include surface roughness, normal force, and surface area.
• Surface roughness increases friction, while polishing surfaces can reduce it.
• The greater the normal force, the greater the friction.
• Increasing the surface area in contact also increases friction.
• Friction can be reduced by using lubricants, polishing surfaces, or reducing the normal force.

Test your understanding of gravity, a universal force that attracts objects with mass, and its effects on Earth and beyond.