Unit 5: Energy and Momentum- Laws of Conservation Flashcards
(16 cards)
What is work?
The energy that a force gives to an object when the force moves the object.
What is positive work?
- When the applied force is in the same direction as the object’s displacement.
- Also occurs when the direction of the object’s displacement is between 0 degrees and 90 degrees to the applied force.
What is negative work?
- When a moving object slides to a rest.
- Negative work happens when an object moves in a direction opposite to the applied force, say due to friction.
- Negative work causes a loss of kinetic energy. Forces that cause negative work are exerted at angles between 90 degrees and 180 degrees opposite to the object’s direction.
What is zero work?
- When the direction of the object’s displacement is exactly 90 degrees to the applied force, the force does zero work.
- There is zero work done by an object when any of the force, displacement, or the cosine of the angle between the force and the displacement is zero.
What is energy?
The ability to do work.
What is kinetic energy?
Energy associated with motion.
What is potential energy?
Energy associated with position. It is the stored energy that an object has that can be released into another form of energy.
What is the work-energy theorem?
When a net force acts on an object the object accelerates. In other words, the force does work on the object and the object’s kinetic energy changes.
What is gravitational potential energy?
The energy stored as the result of the vertical position (height) of an object. Gravitational energy is always measured relative to a position or reference point.
What is the law of conservation of energy?
Energy is neither created nor destroyed, it simply changes forms. Thus, the sum of the kinetic energy and potential energy in any (isolated or closed) system remains constant.
What is the relationship between kinetic energy and potential energy?
As one form transforms into the other work is done. Ex) Basketball is picked up and then dropped.
What happens when only conservative forces (like gravity) work on an object?
Total mechanical energy is conserved.
What happens when nonconservative forces (like friction, air resistance) are at work?
- The total mechanical energy is changed.
- If the work is positive, then the object will gain energy.
- If the work is negative then the object will lose energy.
What is power?
The rate at which work is done.
What is momentum?
The quantity of motion that an object has. It depends on the mass and velocity of an object.
