Physics
Chapters 10 & 11 Outline
Work, Energy, and Simple Machines
Overview - Work-energy theorem. The concept of power. Conservation of energy. Simple machines. Forms of energy.
Objective: - Understand the relationship between work, energy and power. Understand the concept of conservation of energy in its many forms. Calculate work, kinetic and gravitational energy and apply the work-energy theorem.
Start Date: - March 31, 2003
Due Date: - April 8, 2003
Suggested Timeframe: - Lesson begins March
31st.
Labs will be on April 3rd and 4th. Study Guides due April 4th. Homework due
April 7th. Review April 7th..
Test on April 8th
Assignment: - Work and Energy (Chapter 10)
-Work is the product of the force exerted on an object and the distance the
object moves in the direction of the force
-Work is the transfer of energy by mechanical means
-Power is the rate of doing work. That is, power is the rate at which energy is
transferred. It is measured in Watts.
Machines
-Machines, whether powered by humans or engines make work easier. A machine
eases the load either by changing the magnitude or the direction of the force
exerted to do the work.
-The mechanical advantage, MA, is the ratio of the resistance force to the
effort force.
- The ideal mechanical advantage, IMA, is the ratio of the displacements. In
all real machines, MA is less than IMA.
ENERGY (Chapter 11)
Energy in its many forms
-Kinetic energy is the energy an object has because of its motion.
-Potential energy is the energy an object has because of its position, shape or
form.
-According to the work-energy theorem, the work done on an object by the net
force acting on it is equal to the change in kinetic energy of the body.
-Gravitational potential energy depends on the weight of the body and its
separation from earth: PE=mgh.
Conservation of Energy
-The sum of kinetic and potential energies of a system is called the mechanical
energy.
-According to the law of conservation of energy, the total energy of a closed,
isolated system is constant.
Within the system, energy can change form but the total energy does not change.
-In an elastic collision, the total momentum and kinetic energy of a system is
the same before and after the collision.
-In an inelastic collision, momentum is conserved; total kinetic energy is
decreased.
Web Resources:
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