Flash Card #10
What is work?
when the object moves in the same direction in which the force is exerted.
What is the formula for work?
Work=ForcexDistance
What is power?
The amount of work done on an object in a unit of time.
What is the formula for power?
Power=Work over Time
What is a machine?
is a device that allows you to do
work (Wi) easier or more effectively.
What are the three factors that make machines work easier?
1] the amount of force you exert (input force, Fi)
2] the distance over which you exert your force
(input distance, Di)
3] the direction in which you exert your force
(input direction)
What is the formula for machines?
W = F x D
What are levers?
rigid bar that pivots/rotates on a fixed
point.
What is a fulcrum?
fixed point that a lever pivots
around.
How do machines work?
Fi x Di = Fo x Do where i= input, o = output
Fi = Fo x Do
Di = Fo x Do
Di
Fi
Fo = Fi x Di
Do = Fi x Di
Do
Fo
What is mechanical advantage?
the number of
times a machine increases the input force (Fi).
MA = Fo
Fi
What is efficiency?
compares output work to input work.
An ideal machine’s efficiency = 100%. A real
machines efficiency is less than 100% because
some output work (Wo) is lost due to friction (heat
loss).
Efficiency = W0 x 100 = ______ %
Wi
What is a wheel and Axle?
two circular/cylindrical objects
that are connected together and rotate around
a common axis, where:
Wheel: larger radius object
Axle: smaller radius object
What is a pulley?
a grooved wheel with a rope (cable)
wrapped around it.
What are the types of pulleys?
Fixed Pulley, Movable Pulley and Block & Tackle
What is a fixed pulley?
pulley attached to a structure
(ceiling, wall). Fi = Fo , change in direction; MA = 1
What is a movable pulley?
pulley attached to moving object.
increase Fo , no change direction; MA = 2
What is a block and tackle?
fixed & movable pulley system.
increase Fo , no change direction; MA = varies
What is a compound machine?
a combination of two or
more simple machines.
What is energy?
ability to do work
What is chemical energy?
from chemical bonds
What is electrical energy?
moving electrons
What is mechanical energy?
moving things (parts)
What is heat energy?
moving molecules
What is nuclear energy?
from atom’s nucleus
What is light(solar) energy?
moving photons
What is sound energy?
vibrating objects
What is potential energy?
stored energy
What is kinetic energy?
motion energy
What is the formula for potential energy?
Stored energy; energy of position
PE = weight (mass) x height
What is the formula for kinetic energy?
motion energy
KE= 0.5 mass x velocity2
Potential
(work)
Kinetic
Work (joule) = Force (newton) x Distance (meter)
What are renewable resources?
are materials that
can be replaced at the rate at which we use
them.
What are non-renewable resources?
are materials
that can not be replaced at the rate at which we
use them.
