What is it?How is it calculated?How is it measured?

Work

New TermsWork – a force applied over a distance.Joules (J) – SI unit for work. 1 J = 1 N*m so,

a Joule is equal to a force of 1 N acting over a distance of 1 m.

Foot Pound-Force – English unit for work. Used in engineering fields commonly. 1 ft-lb is equal to 1.36 J.

Work ExamplesTo have work in science, BOTH a force AND

a distance NEED to be involved!Holding 300 pounds still over your head is

hard, but is NOT an example of work.Lifting the weight is, pushing a chair is,

work is done to move an elevator from the first floor to the 5th floor.

Work Examples, cont.Which example shows work being done?Depends. They both have a force. Which

one has movement (the animation isn’t working on the website)?

Calculating WorkFormula Work = Force x DistanceUnits: Work is in Joules, Force is in

Newtons and Distance is in MetersExample: How much work is done moving a

couch with a force of 500N a distance of 10m?

Answer to Previous QuestionW = ? JF = 500 ND = 10 MSo, W = FdW = 500 x 10W = 5000 J (Joules can be written as N*m,

so the answer could be 5000 N*m)

More CalculationsWork = F x d, F = m x a, a = v/t, v = d/tYou can calculate work if given a distance,

a time, and a mass.How much work is done moving a 5kg

object 2m in 10s?

Problem SolutionStep 1: Calculate v. V= 2/10. V=0.20 m/sStep 2: Calculate a. A=(0.2-0)/10. A=

0.02m/s2

Step 3: Calculate F. F=5x0.02. F=0.10NStep 4: Calculate W. W=0.10x2. W=0.20J

Assessment1. What is the SI unit of measurement for

work?

2. How far would a person need to move an object to exert 500J if the object required 125N to move?

3. How much force does it take to move a bed 10m if 150,000J are used moving the object?

Answers1. Joule (J)

2. 4m

3. 15,000N