PHY 5 - Work Flashcards
If displacement is zero, what is the work done ?
0.
Work done = Force x distance moved in direction of force
Why would you include Cos Ø to the work equation ?
To take into account that the force applied is not always at the same angle to the displacement. By using Cos Ø you seperate the force into vetical and horizontal components using the adjacent side.
What are the units of work ?
1 Joule (J) = 1 newton over 1 metre
Describe energy in terms of physics ?
Energy is a scaler, it is a physical quantity capable of producing work.
Name 8 different types of Energy
- Mechanical
- Electrical
- Chemical
- Potential
- Kinetic
- Sound
- Atomic
- Nuclear
What happens to the work done if the displacement is at 90º to the force ?
0 Work done because Cos 90 = 0.
What is the work done by the force normal ?
It is a counter-active force, therefore no work is done.
Describe the work done by friction ?
Always acts opposite to the direction of motion, Cos 180 º always = a negative value.
What equation summarises kinetic energy ?
What equation is described by the work-energy theorem ?
Change in kinetic energy + change in potential energy = Work
What is the equation for potential energy derived from the gravitation forces ?
Potential Energy = mgh
m = mass
g = gravity
h = height
Explain mechanical energy in relation to frictional forces ?
They are non-conservative forms of mechanical energy
What causes friction ?
Molecular adhesion between tangential surfaces- it is independent of the area of the surfaces touching each other.
What direction do frictional forces work on ?
They always oppose the motion
Name the two types of friction
- Static
- Kinetic
What is static friction ?
When the object is not moving, static friction is the force that must be overcome in order to move it.
Describe friction ?
A contact force that acts to oppose sliding motion between surfaces.
Explain when friction would be high or low ?
Increased if surfaces are dry and rough
Decreased if surfaces are wet and smooth
What is the Force Normal ?
The force perpendicular to the surface, typically equal and opposite to the gravitational force.
What is the coefficicent of friction ?
It is defined by the materials from which the two surfaces are made, and the relative roughess of the surfaces in contact.