Rearranging Power Equations for Calculating Power
Learn how to mathematically rearrange power equations and calculate power using relevant formulas. Understand the relationship between power, work, and time through examples and explanations in this informative guide.
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Presentation Transcript
Rearranging Power Equation and teach examples
Learning Objectives I can mathematically rearrange the power equation. I can calculate power using the formula.
Calculating Power Power = work divided by time P = ? Watts joules ? seconds Power is the rate at which work is done.
Formula Representation Formula Represents Power Units P = W = Work T = Time Watts (W) Joules (J) Second (s) P = ? ?
Solve for Work (W) Solve for Work (W) Step 1 Multiply both sides by t - time P = ? (t) (t) ? W = Pt
Solve for Time (t) Solve for Time (t) Step 1 Multiply both sides by t time P = ? (t) (t) ? W = Pt Step 2 Divide by P - power on both sides. __ P __ P t = ? ?
Power Related Equations Power P = ? Work Time t = ? W = Pt ? ?
Calculation Example #1 1. A weightlifter lifts a barbell in 3s and does 2,400J of work. How much power was used to lift the barbell? Given/ Unknown P = W = t = Work ? 2,400J 3s 2,400j 3s P =W P = 800W P = t
Calculation Example #2 2. A student rows a boat across a still pond, using a power of 60W and takes 60s. What is the work done by the student? Given/ Unknown P = W = t = Work 60W ? W = 3600J W = (60W) 60s W = Pt 60s
Calculation Example #3 3. The power of a small motor is 180W and will do 4500J of work in how much time? Given/ Unknown P = w = t = Work 180W 4500J ? t =W 4,500j 180W t = 25s t = P
Calculation Example #4 4. A crane lifts a 35,000N steel girder a distance of 15m in 1minute. How much power did the crane require to lift the girder? Write your answer in kilowatts Given/ Unknown P = f = t = d = 15m Work 1min=60seconds ? 1st convert the time into seconds 35,000N 1min (35,000N)(15m) 60s P =W or (fd) P =525,000J P = 8750W or 60s P = t 60s 2nd convert the watts to kilowatts 1000w = 1kw P = 8.750kW
