First we learned...
Work and Power:
Work = Force x Distance
Work is measured in joules
The force and distanced used to calculate the work you do on something must be parallel. For instance is a box weighs a certain number of Newtons(upwards), and you take it across the room(forward), then you don't do work on the box.
Work is fairly similar to what you may think it is. The only misleading thing about our idea of work is that sometimes we may feel as though we are putting more or less work in when the work is actually the same.
One way it is misleading is that you may get tired doing work faster and thus think you have done more work. This isn't more work, it is more power.
Power is the time in which you do work. Power is measured in watts.
(Power = Work / time)
So, if you do something faster an end up feeling more tired, you just used more power, your work probably didn't change.
Note: 746 watts = one horsepower.
We then learned that Work is also related to Kinetic Energy:
Kinetic Energy is basically energy that a moving object has.
the formula is:
KE = (1/2)m(v)^2
So, you can calculate the KE for anything that you know has mass and velocity. (an object that is not moving does not have KE. Neither does an object with no mass.)
What we learned is that the change in KE is equal to Work
change in KE = Work
Often, we will calculate the change in KE in an object that speeds up or slows down over a distance(the velocity changes). We can jump between Work and KE(and then power if we know the time) by subtracting the final KE from the initial KE and then finding the Force by plugging it into Work = Force x Distance using the distance it changed KE.
Once we learned about Kinetic Energy, we learned about Conservation of Energy:
We learned that, when an object moves(or doesn't), it does not lose energy. The energy may be lost to heat or sound or light, however it is all accounted for. You also do not add Energy.
An example is when an object is swinging on a string. When it is at the top of it's path(and it may be a t rest), it has a lot of Potential Energy but no Kinetic Energy. When it swings down, it starts to lose potential energy and gain Kinetic Energy until at the nadir of the path, it has a lot of Kinetic Energy and no Potential Energy. This relationship, in fact, is equal and opposite.
change in KE = change in PE
You could relate this to the law of conservation of momentum because in a given situation(like an airbag in a car), you could use the fact that the change in momentum/energy is always the same to determine the factors that increase or decrease your injury in a car crash.
With these added equations, we add on to the amount of steps we could use to go from, say, PE to Work. We could use PE = KE, and then use KE = Work to find, say, distance or force.
To Apply these to actual actions, we talked about Machines:
Specifically, simple machines.
Three types of simple machines are:
a ramp, a pulley, and a jack(for a car).
The way Machines work is they increase the distance over which the work is done so that the force is decreased and it feels easier. This is a way in which what we are doing can feel deceiving because we may be tempted to say that the work decreases because it feels easier. However, it is rather the case that
Work in = Work out
F(D) = F(D)
For instance, a ramp with increase the distance of the work you put in which makes the force you put in less. However, it still equals the same work out regardless.
We did a podcast on Machines which includes some helpful examples about how machines work and how efficient they are. Watch below to learn more.
Thanks for reading!
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