Lecture Five Flashcards
(11 cards)
What is Newton’s second law of motion?
Force = mass x acceleration
OR – Force = rate of change in momentum
What is Newton’s first law of motion?
An object moves at constant velocity unless a net force acts to change its speed or direction
Newton’s third law of motion?
For every force, there is always an equal and opposite reaction force
Why do objects move at constant velocity if no force acts on them?
Conservation of momentum:
- The total momentum of interacting objects cannot change unless an external force is acting on them.
- Interacting objects exchange momentum through equal and opposite forces.
What keeps a planet rotating and orbiting the Sun?
Conservation of Angular Momentum:
- Angular momentum = mass x velocity x radius
- The angular momentum of an object cannot change unless an external twisting force (torque) is acting on it.
- Earth experiences no twisting force as it orbits the Sun, so its rotation and orbit will continue indefinitely.
Types of energy?
Kinetic - motion
Radiative - light
Potential - stored
What is thermal energy?
The collective kinetic energy of many particles. It depends on temperature and density.
What is temperature?
the average kinetic energy of the many particles in a substance
Gravitation potential energy on earth depends on:
- object’s mass (m)
- strength of gravity (g)
- distance object could potentially fall
Conservation of mass-energy
Mass itself is a form of potential energy: E= 2 mc
When the Sun shines it loses mass
Concentrated energy can spontaneously turn into particles (for example, in particle accelerators).
Conservation of energy
- Energy can be neither created nor destroyed
- It can change form or be exchanged between objects
- The total energy content of the universe was determined in the Big Bang and remains the same today
