Mechanics 4 - Work, Energy and Power Flashcards
What is the principle of conservation of energy?
Energy cannot be created or destroyed, only transferred from one type to another.
How does an object gain energy from a force?
When the force does work on the object (same direction as movement)
How does an object lose energy?
By doing work against a force (usually frictional)
What’s wrong here?
In W=Fs you multiply the parallel components
When using W=Fs what must be the case?
The components must be parallel
What is the work done by the weight of this block?
0 because the weight is perpendicular to the movement
So there is no parallel component to displacement
If two objects are dropped from the same height and air resistance is negligible, which hits the ground first?
Both hit at the same time because they both accelerate at 9.81ms-2
How do you calculate the velocity the object hits the ground using GPE and KE (assuming no air resistance)
Energy equivalency (only works when air resistance = 0)
What is power?
The rate of transfer of energy
or
The rate at which work is done
(Measured in Watts [W])
What is wrong here?
For P=Fv, F is not the resultant force
How do you calculate efficiency?
If the system is not 100% efficient would this be correct?
No, because some GPE is converted to thermal and kinetic energy of the snow (working against friction)
