Unit Energy Module Work page 1 of 1 The Work Done by a Constant Force in One Dimension In one dimension work is the product of the force applied to the object and the displacement of the object W Fx x Work is a scalar not a vector The unit of work is the Joule J 1 J 1 Nim 1 kgim2 s2 If force and displacement are in the same direction work is positive If force and displacement are in opposite directions work is negative If you push a heavy cart it feels like you are doing work Work is the product of the force applied to an object and the displacement of the object If the force applied to an object and the displacement of the object are both in the same direction the work done on the object is positive This is illustrated in the top two examples If the force applied to an object and the displacement of the object are in opposite directions the work done by the object is negative This is illustrated in the bottom example Notice that work is a scalar not a vector The unit of 1 kgim2 work is the Joule J 1 J 1 Nim s2 A car skids to a halt across 20 m of pavement The car has a mass of 1000 kg and the coefficient of kinetic friction for the pavement is 0 8 You would like to know how much work was done by friction on the car Work is the product of the force applied to the car by kinetic friction and the displacement of the car W fk x In this example Kinetic friction is slowing the car down it is in the negative direction fk k N Since there is no acceleration in the vertical direction the normal force is mg The work done by friction on the car is 160 000 J A 1 kg weight is lifted half a meter with constant velocity What is the work done by gravity on the weight If up is the positive direction then the force of gravity is in the negative direction mg The displacement is 0 5 m in the positive direction The work done by gravity on the weight is 4 9 J www thinkwell com info thinkwell com Copyright 2001 Thinkwell Corp All Rights Reserved 1930 doc rev 03 27 2001
View Full Document
Unlocking...