UNIT E: Mechanical Systems Flashcards
What is the formula for work?
force x distance
What is the formula for speed ratio?
load force / effort force
effort arm / load arm
What are the formulas for mechanical advantage? Are there units?
driver teeth / # driven teeth
No units
What are the formulas for efficiency?
output force / input force x 100
MA / SR x 100
What is the formula for pressure? What are the units?
force / area
UNITS: f - N, A - m2, P - Pa or N/m2
What is a machine? Give an example.
Any device that helps to do work. i.e. hairbrush
What’s the difference between systems and subsystems?
Subsystem - a system of its own i.e. wheel and axle
System - subsystems put together
Give 3 examples of energy sources for machines.
Human force, wind, fossil fuels.
How do gears transfer energy?
The teeth mesh together and transfer energy through rotation.
What is the difference between potential and kinetic energy?
Potential: stored energy
Kinetic: energy in motion
What is efficiency?
A measure of how well a machine uses energy.
More energy being lost = less efficient
The work done by a ramp is 1350J, and the work done by the effort force is 2134J. What is the efficiency of the machine?
1350/2134 x 100 = 63.26%
What si friction? How do you reduce it?
Force applied in opposite direction; a resistant force.
Can be reduced with oil/grease
What are the 6 types of simple machines?
Lever
Inclined plane
Wedge
Screw
Pulley
Wheel & axle
What is mechanical advantage?
Comparison of force produced by machine and force applied to machine
How are pulleys and levers alike?
Both lift objects, use a rotational movement.
Describe fluid pressure.
the force per unit area on a specific item on the surface of a closed container.
How are forces transmitted in all directions?
Pascal’s law says pressure applied to an enclosed fluid is transmitted equally.
How does hydraulic pressure create MA?
allows to use a small force on a small piston to produce a larger force on the large piston.
Does shape have effect on pressure?
No
Can machines be 100% efficient? Why or why not?
They cannot, work is always lost through friction and heat
