Topic 8+9 - Forces doing work + forces and their effects Flashcards
Energy is never ______ nor _____, it is only _______
a) created
b) destroyed
c) transferred
What is a closed system
A system in which no external forces are experienced
Formula for gravitational potential energy (closed system)
∆GPE=mgh
where m=mass(kg), g=gravity(N), h=height above surface
What is the formula for a closed system
KE=1/2 mv^2
where m=mass, v=velocity
What is work done
When an external force transfers energy into a system
Give an example of work done
A person doing work to push a ball up a hill
What is the force for work done
E=fd
Where, N=force, d=distance (m)
What is power
The rate at which energy is transferred
What is the formula for power
P=e/t
Where, e=work done, t=time taken (s)
What is effiency
Measure of how much energy is not lost as waste
What is the formula for efficiency
efficiency = useful output energy / total input energy
What is the principle of moments
When a body is balanced, the total CLOCKWISE moment around a pivot is equal to the total ANTICLOCKWISE moment
Give examples of an object interacting at a distance without contact
- Gravitational attraction
- Electrostatic attraction
- Magnetic attraction
Give examples of an object interacting at a distance with contact
Every force that is not the magnetic, electrostatic or gravitational attraction
What does a vector have
Size and direction
What does a scalar have
Just size
What do free body diagrams have
The direction of forces that are present in a situation
If an object is attached to a pivot point, what can happen
It can rotate around but not move away from the pivot
If a force is applied not towards the point, what happens
The object will not rotate
If the force is applied perpendicular to the object what will happen
It will move about the pivot in this direction
What is the formula for a moment
M=Fd
Where F=force, d=distance in m
What will happen if a gear with fewer teeth is connected to a gear
The second gear will turn faster, with less force and in the opposite direction to the first gear
if the gear is connected to a gear with more teeth, what will happen
The gear will move slower with more force in the opposite direction
