CHAPTER 5Work and Machines

DEFINITIONS

Effort Force- (Fe) the force put into a machine

Resistance Force- (FR) the force moved by a machine

Weight is a force. F = ma (mass in kg) (acceleration of gravity)

Energy- the ability to do workMeasured in Joules

Mechanical Advantage- the number of times a machine multiplies the force or work put into a machine

Formulas

Work = Force x distance W = F x d

1 Nm = 1 Joule

Power = Work / time P = W / t

1 Watt = 1 J/s = 0.239 cal/sec

Efficiency = (WOUT) / (WIN) x 100%

Levers

MA = (Length of effort arm) / (Length of Resistance arm)

MA = Le / LR

Inclined Plane

MA = (Length of slope) / (height of slope)

MA= l / h

Wheel and Axle

MA = (radius of wheel) / (radius of axle)

MA = rW / ra

Gears

A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque

Torque- a rotating force

Pulleys

Fixed Pulley

MA = 1

Moveable Pulley

MA = LE / LR

Block & Tackle

MA = Number of ropes in the system

Wedges and Screws

USE YOUR NOTES TO STUDY FOR THE CH. 5 TEST WEDNSEDAY FEB 9th

TODAY’S ASSIGNMENT IS DUE MONDAY FEBRUARY 7th