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Work What is it? How is it calculated? How is it measured? New Terms Work – 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 Examples To 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 Work Formula Work = Force x Distance Units: Work is in Joules, Force is in Newtons and Distance is in Meters Example: How much work is done moving a couch with a force of 500N a distance of 10m? Answer to Previous Question W=?J F = 500 N D = 10 M So, W = Fd W = 500 x 10 W = 5000 J (Joules can be written as N*m, so the answer could be 5000 N*m) More Calculations Work = F x d, F = m x a, a = v/t, v = d/t You 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 Solution Step 1: Calculate v. V= 2/10. V=0.20 m/s Step 2: Calculate a. A=(0.2-0)/10. A= 0.02m/s2 Step 3: Calculate F. F=5x0.02. F=0.10N Step 4: Calculate W. W=0.10x2. W=0.20J Assessment 1. 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? Answers 1. Joule (J) 2. 4m 3. 15,000N