Mass

Definition

Mass is a measure of the amount of matter in an object, typically measured in kilograms or grams. It is a fundamental property of physical objects that affects how they respond to forces, particularly in the context of motion and gravitational attraction. Mass plays a crucial role in understanding the relationships between force, acceleration, and gravitational pull, influencing how objects move and interact with each other.

5 Must Know Facts For Your Next Test

1. Mass is an intrinsic property of matter and does not change regardless of location, unlike weight, which can vary depending on gravitational force.
2. In Newton's first law, an object at rest stays at rest and an object in motion continues in motion unless acted upon by a net external force, highlighting the role of mass in inertia.
3. According to Newton's second law, acceleration produced by a net force on an object is inversely proportional to its mass (a = F/m), indicating that more massive objects require more force to achieve the same acceleration as less massive objects.
4. Mass also affects gravitational attraction; larger masses exert a stronger gravitational pull on other masses, described by Newton's law of universal gravitation.
5. In the context of relativity, mass and energy are related through Einstein's famous equation E = mc², indicating that mass can be converted into energy.

Review Questions

• How does mass influence an object's resistance to changes in motion according to Newton's laws?
  • Mass plays a key role in an object's resistance to changes in motion through the concept of inertia. According to Newton's first law, an object will remain at rest or continue moving at a constant velocity unless acted upon by a net external force. The greater the mass of the object, the greater its inertia, meaning it requires more force to change its state of motion, whether starting from rest or altering its velocity.
• Discuss the relationship between mass and gravitational force as described by Newton's law of universal gravitation.
  • Newton's law of universal gravitation states that every point mass attracts every other point mass 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. This means that as the mass of either object increases, the gravitational attraction between them also increases. Thus, mass directly influences how strongly objects interact with each other gravitationally.
• Evaluate how the concept of mass differs between classical mechanics and relativistic physics.
  • In classical mechanics, mass is viewed as a fixed quantity that determines an object's resistance to acceleration and its gravitational attraction. However, in relativistic physics, as described by Einstein’s theory of relativity, mass is not just a measure of matter but is intricately linked to energy through E = mc². This means that as an object's speed approaches the speed of light, its relativistic mass increases, requiring more energy for further acceleration. This shift from a static understanding of mass in classical mechanics to a dynamic relationship with energy in relativity reflects deeper insights into the nature of matter and motion.

Related terms

weight: Weight is the force exerted on an object due to gravity, which is the product of its mass and the acceleration due to gravity (weight = mass × gravity).

inertia: Inertia is the tendency of an object to resist changes in its state of motion, directly related to its mass; greater mass means greater inertia.

force: Force is any interaction that causes an object to change its velocity, which is defined by Newton's second law as force = mass × acceleration.