chapter 2: work and energy

The property of a system that enables it to do something or make something happen, including the capacity to do work

Energy

Energy associated with the movement of objects. It depends on mass and speed squared (not velocity).

Kinetic energy

Energy stored within a system. It exists in gravitational; elastic, electrical, and chemical forms.

Potential energy

Related to the mass of an object and its height above a zero-point, called a datum.

Gravitational potential energy

Related to the spring constant (a measure of stiffness of a spring) and the degree of stretch or compression of a spring squared.

Elastic potential energy

Electrical potential energy exists between charged particles.

electrical potential energy

The energy stored in the bonds of compounds

Chemical potential energy

path independent and do not dissipate the mechanical energy of a system.

conservative forces

If only conservative forces are acting on an object, the total mechanical energy is …

Conserved.

path dependent and cause dissipation of mechanical energy from a system.

nonconservative forces

A process by which energy is transferred from one system to another.

Work

The rate at which work is done or energy is transferred.

Power

The factor by which a simple machine multiplies the input force to accomplish work.

Mechanical advantage

The six simple machines

inclined plane, wedge, wheel and axle, lever, pulley, and screw

Mechanical advantage makes it easier to accomplish a given amount of work because the input force necessary to accomplish the work is …

Reduced

The output force of a simple machine, which acts over a given load distance to determine the work output of the simple machine.

The load

The ratio of the machine's work output to work input when nonconservative forces are taken into account.

Efficiency

the input force of a simple machine, which acts over a given effort distance to determine the work input of the simple machine.

the effort

kinetic energy equation

K = ½ mv²

gravitational potential energy equation

U = mgh

elastic potential energy equation

U = ½ kx²

total mechanical energy equation

E = U + K

conservation of mechanical energy equation

ΔE = ΔU + ΔK = 0

definition of work (mechanical) equation

W = f(dot)d = Fdcosθ

definition of work (isobaric gas-piston system) equation

W = PΔV

definition of power equation

P = W/t = ΔE/t

work-energy theorem equation

Wnet = ΔK = Kf - Ki

mechanical advantage equation

mechanical advantage = (Fout)/(Fin)

efficiency equation

efficiency = (Wout)/(Win) = ((load)(load distance))/((effort)(effort distance))