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The Science of Physics

The Science of Physics. The Language of Physics. Mathematics and Physics. Physicists use mathematics to analyze and summarize their observations Use mathematical relationships among physical quantities to help predict what will happen in new situations Use tables, graphs, and equations.

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The Science of Physics

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  1. The Science of Physics The Language of Physics

  2. Mathematics and Physics • Physicists use mathematics to analyze and summarize their observations • Use mathematical relationships among physical quantities to help predict what will happen in new situations • Use tables, graphs, and equations

  3. Mathematics and Physics • Physics equations indicate relationships • Use letters to describe specific quantities • v often stands for velocity or speed • Variables use bold or italics to distinguish them from units which use regular type • Greek letters often describe a mathematical operation • Delta (Δ) means “difference” or “change in” • Subtraction • Sigma (Σ) means “sum” or “total” • Addition

  4. Direct Proportions • Directly proportional – when dividing two sets of quantities by one another gives a constant value • Graphs as a straight line that passes through (0,0) • Can be expressed y x which reads y is proportional to x • y/x=k or y=kx. • When x increases, y increases and vice versa

  5. Inverse Proportions • Inversely proportional – when two sets of quantities have products that are constant • Graphs as a curve called a hyperbola • Can be written as y 1/x which can be read as y is proportional to one divided by x • xy=k • When x increases, y decreases and vice versa

  6. Dimensional Analysis • Treat dimensions like algebraic variables • Can rearrange them in equations by performing the same operation to both sides v = d / t Solve for t

  7. Dimensional Analysis • v = d / t • Multiply both sides by t t * v = d / t * t t’s on the right side cancel out t * v = d

  8. Dimensional Analysis • t * v = d • Divide both sides by v • (1 / v) * t * v = d * (1 / v) • v’s on the left side cancel out • t = d / v • Plug in numbers

  9. Order-of-Magnitude • Gives you a ballpark estimate • Useful if you don’t have a calculator • Use power of 10 closest to actual numbers instead of actual numbers • d = 725km • v = 88km/h • t = ?

  10. Order-of-Magnitude • d = 725km ≈ 1000km • v = 88km/h ≈ 100km/h • t = d / v

  11. Order-of-Magnitude • t ≈ 1000km / 100km/h ≈ 10h • t = 725km / 88km/h = 8.2h

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