how machines do work
DESCRIPTION
How Machines do Work. Mechanical Advantage and Efficiency. What is a Machine?. Shovel Wheelbarrow Bulldozer Rake. A machine is a device that makes work easier! Amount of work does not change!. What is a Machine?. 2 Types of Machines. Simple Unpowered mechanical device There are 6: - PowerPoint PPT PresentationTRANSCRIPT
How Machines do Work
Mechanical Advantage and Efficiency
What is a Machine?
0 Shovel0 Wheelbarrow0 Bulldozer0 Rake
What is a Machine?
0A machine is a device that makes work easier!0Amount of work does
not change!
2 Types of MachinesSimple
0Unpowered mechanical device0There are 6:
0Lever0Pulley
0Wheel and Axle0 Incline Plane
0Screw0Wedge
Compound0A machine that has two or
more simple machines
Input Force0The force YOU PUT INTO the machine is called the
input force.
0It is also called the EFFORT force
0In other words: The input includes everything you do to make the machine work.
Input Force
Output Force0The force done by the machine is called the
output force.
0Also called the RESISTANCE
0In other words: The output is what the machine does for you.
Output Force
Force/Distance Trade Off0Mechanical Advantage: how many times the
machine increases your force 0(how much the machine makes work easier)
0A machine can make work easier by changing either:0Direction0Distance 0Force
0The amount of work stays the same!!
Changing Direction0When a machine changes the direction of the
input force, the amount of force and distance remain the same
InputDirection
Output Direction
Changing Distance0If you want the machine to increase your distance,
you must apply more force over a shorter distance.
0Force (F) x distance (d) = Work (W) = Force (F) x distance (d)Input Distance
OutputDistance
Changing Force0 If you want the machine to help you use less
force, you must apply the smaller force over a longer distance.
0Force (F) x distance (d) = Work (W) = Force (F) x distance (d)
Efficiency of Machines
0The efficiency of a machine tells how well the machine works
0Efficiency is always a percent.
0The higher the percent, the more efficient the machine is.090%075%050%
Input and Output Work0Friction always converts some of the input work to heat
and wear, so the output work is always less than the input work.
0The more friction in a machine, the less efficient the machine!
More
Less
Real vs. Ideal Machines0An ideal machine would have an efficiency of 100%.
0However, all real machines have an efficiency of less than 100% because some work is wasted due to friction.