Physics Test 6 Vocab

Work

Force in the direction of the displacement

A force exerted through a distance performs mechanical work.

Joule

Units: The unit of Force is the Newton. Unit of displacement is the meter. Thus, the unit for work is the Newton - meter. We define a joule, J as:

1 J = 1 Nm

We can break the definition of joule into basic kg, m and s units as: 

1 J = 1 Nm = 1 (kgm/s2)m = 1 kgm2/s2 

Kinetic Energy

In general, the kinetic energy of an object is the energy due to the object's motion.

Unlike work, K is always greater than or equal to zero (there is no negative kinetic energy).

Power

Power is a measure of how quickly work is done. We define average power as the total work done divided by the time it takes to perform the work.

Work-Energy Theorem

 states that The work done equals the change in kinetic energy.

Potential Energy

Potential Energy is stored energy. When a conservative force does an amount of work, W_c, the corresponding potential energy, U is changed

Mehcanical Energy

as the sum of the potential and kinetic energies of an object.

Nonconservative work

the work done by a non-conservative force

Conservative work

the work done by a conservative force

Conservative forces

When a conservative force acts, the work the force does is stored in the form of energy that can be released at a later time. (gravity and springs)

Non conservative forces

Nonconservative forces change the amount of mechanical energy in a system. They might decrease the mechanical energy by converting the energy to thermal energy or take muscular work to increase kinetic or potential energy in a system. (friction, air resistance, and push-pull forces)

Conservation of Mechanical Energy

Now that we have introduced both kinetic energy, K (the energy of motion) and potential energy, U (the energy of position), we can define mechanical energy, E as the sum of the potential and kinetic energies of an object. In systems with only conservative forces, the mechanical energy, E, is constant.