3.3 Work, energy and power Flashcards
3.3.1 Work and conservation of energy, 3.3.2 Kinetic and potential energies, 3.3.3 Power (19 cards)
What is the unit of work done?
The Joule.
How do you calculate the work done when there is an angle Θ (Theta)?
W=F x cosΘ . F is the force, x is the distance moved. theta is the angle between the force vector and the displacement vector.
What is the equation for work done if the object moves in the same direction as the force?
W=Fd
True or false: if an object moves perpendicular to the force, no work is done.
True
On a force displacement graph, what is the area underneath equal to?
work done
What is the principle of conservation of energy?
Energy cannot be created or destroyed, just transferred between stores and objects.
What is gravitational potential energy?
When an object is in a gravitational field, if it moves up the gp energy store increases. Gpe decreases when an object moves down.
How do you calculate gpe?
Ep=mgh
How do you calculate kinetic energy?
Ek= 1/2mv^2
T or F: transfer of energy is equal to the work done
T
How to derive Gpe?
W=Fx, W=Energy, Ep=Fx, mg= weight which is a force so Ep=mg x, where x is the distance so in this case its height. Ep=mgh
How to derive kinetic energy?
F=ma, so W=max, W= an energy, Ek=max. v^2=u^2+2as. v^2-0/2x=a, Ek=mv^2/2
when is mgh=1/2mv^2 true?
Falling objects, objects kinetic energy after falling through a height is equal to its loss of Gpe.
When is mgh=1/2mv^2+F x true?
Sliding objects, when an object slides a distance x down a slope, losing vertical height, the objects loss of gpe is equal to its kinetic energy plus energy lost due to the work done by friction.
What is power?
the rate of energy transferred or work done.
What is the equation linking power, time and work done?
P=W/t
What is the unit of power?
Yes lol, watt
What is efficiency?
is a measure of how much energy is wasted in an energy transfer.
How to derive P= Fv from P=W/t and W=F x.
P=W/t, W=Fx, V=displacement/time. P=Fx/t, P= F * x/t , P=Fv
