Unit 5

Work and Power

Work is the measurement of force * the distance and is measured in Joules, work can only be present if the force and the distance are parallel to each other, . For example if you are climbing up a stair the distance will be the vertical height of the stairs and the force would be your weight. Power is how much work is done in a period of time Power = work/time, and is measured in Watts. For example if a person put in 50J of work in 5 seconds then that is equivalent to 10Watts of power.

Work and Energy Relationship

Work is Equal to the change in Kinetic Energy and is also equal to the change in Potential Energy. So if we know one of them we know the rest, But that does not mean they have the same equation Work is equal to distance * time, and Kinetic Energy is equal to 1/2 mass*velocity^2, and Potential Energy is equal to mass * gravity * height.
Kinetic energy is the energy that has to do with an object moving horizontally, and Potential Energy is the amount of energy an object has at a set height (vertically).
So if an object was on ground level and had a weight of 500N and was going at 5m/s then the object has 2500 Joules.

Conservation of Energy

Energy is neither created nor destroyed. The conservation of energy in similar to the conservation of momentum. You start out and end with the same amount of joules, the only thing different in this case is that the energy changes its form, but is still constant. In a roller-coaster, the first drop is always the highest then the rest do not matter in height as long as they are shorter than the first one. The coaster will keep on going. For example if it started with 1000 Joules of potential energy, when it drops and reaches the ground it still has 1000 Joules but of Kinetic Energy.

Machines

A machine is basically an object which makes it possible for a person to exert little force on an object that needs a big force, but while doing that the distance will also increase making the work similar in both cases  (BigForce*SmallDistance = SmallForce *BigDistance)
Fin * Din = Fout * Dout
Work1 = Work2

If a person where to lift an object straight into a truck and the other uses a ramp, both would be using the same amount of joules, as force the person without a ramp he exerts a big force over a small distance, but with a ramp, the force is smaller with a bigger distance.