Chapter 9 - Energy Flashcards
Work is the product of what two variables?
The net force acting on a object and the distance through which it is moved.
What is power?
The rate at which work is done (or work divided by time)
What are the two forms of mechanical energy we studied?
Kinetic energy and gravitational potential energy
What is the unit of work and energy?
The joule (or Newton-meter)
What is the unit of power?
The watt (or joule/sec)
What is kinetic energy?
The energy an object has as a result of its motion.
The kinetic energy of a moving object is equal to …
The work required to bring it to its speed from rest, or the work the object can do while being brought to rest.
The law of conservation of energy states that energy cannot be ______ or _______. Instead, its transformed from one form to another.
Created or destroyed.
What are the six simple machines?
Pulley, wheel and axle, inclined plane, screw, wedge and lever.
The trade off of using less force with a simple machine is what?
Having to exert that force over a greater distance.
A machine’s efficiency is equal to ________
the ratio of useful work output to total work input
In a complex pulley system, the mechanical advantage equals ________
the number of supporting cables.
If a boulder on the edge of a cliff has 100 J of potential energy, how much kinetic energy will it have when it’s fallen three-quarters of the way to the bottom?
75 Joules
Why can a machine not be 100% efficient?
Loss of energy due to friction.
