Engineering Principles Flashcards
What is the definition of density?
The density of a substance is defined as its mass per unit volume.
Units are Kg/m^3
What is the definition relative density?
Relative density of a substance is the ratio of the the density of that substance compared to the pure density of water.
What is the definition friction?
Friction is the force which opposes the relative sliding motion of two surfaces in contact with each other.
It is measured in Newtons.
What are the two kinds of friction?
- Static friction
-Kinetic friction
What is static friction?
This is friction between surfaces of two stationary bodies on contact with one another.
What is kinetic friction? what are the two types of kinetic friction?
This is friction between surfaces moving relative to one another.
sliding- between two solid surfaces
viscous- between a solid and fluid
What is the coefficient of friction?
The measure of the amount of friction between two surfaces.
What factors can effect friction?
- The nature of the materials in contact
- The perpendicular forces between the 2 surfaces
- The presence/absence of any form of lubricant
What is meant by viscosity?
Viscosity is a measure of a fluids resistance to flow.
What are the consequences of high viscosity?
High viscosity = thick
Increased power losses but reduced wear rate to machinery.
What are the consequences of low viscosity?
Low viscosity = thin
Reduced power losses but increased wear rate to machinary.
Define a simple machine?
A simple machine is a device that is used to change the size/direction of the line of action of an applied force.
What are the four examples of simple machines?
- Pulley system
- Screw jack
- Geared system
-Lever
Define mechanical advantage?
This is the ratio of LOAD to EFFORT required to move it.
What is mechanical Advantage also known as?
force ratio
Define velocity ratio?
This is the ratio of ‘distance moved by EFFORT’ to @Distance moved by LOAD’
What is velocity ratio known as?
movement ratio
Briefly explain how a screw jack works?
The screw of the jack is fixed in the body of the jack. As the table is rotated by the bar, it raises or lowers a load placed on the table.
What is the formula to calculate velocity ratio of a geared system?
Velocity ratio= No of teeth on follower/no of teeth on driver
Define a moment of force
A moment is the turning effect of a force.
Measured in Newton meters.
Define a couple
A couple is a pair of forces, equal, oppositely directed and displaced by perpendicular distance.
What are the two conditions for static equilibrium?
Forces up = Forces down
CWM =ACWM
When multiplying two or more numbers with the same base, what do you do with the indices?
Add them
When dividing two or more numbers with the same base, what do you do with the indices?
Subtract them
