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Introduction to Laplace Transforms

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See 'show steps'.

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Find $L\\{\\var{a} \\}$.

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$L\\{k\\}=\\frac{k}{s}$

", "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "showCorrectAnswer": true, "scripts": {}, "marks": 0, "type": "information"}], "marks": 1, "scripts": {}, "answer": "{a}/s", "showCorrectAnswer": true, "checkvariablenames": false, "checkingtype": "absdiff", "vsetrange": [0, 1]}, {"stepsPenalty": 0, "variableReplacements": [], "prompt": "

Find $L\\{\\var{b}t \\}$.

", "expectedvariablenames": [], "checkingaccuracy": 0.001, "type": "jme", "showpreview": true, "vsetrangepoints": 5, "variableReplacementStrategy": "originalfirst", "steps": [{"prompt": "

$L\\{t\\}=\\frac{1}{s^2}$

", "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "showCorrectAnswer": true, "scripts": {}, "marks": 0, "type": "information"}], "marks": 1, "scripts": {}, "answer": "{b}/s^2", "showCorrectAnswer": true, "checkvariablenames": false, "checkingtype": "absdiff", "vsetrange": [0, 1]}, {"stepsPenalty": 0, "variableReplacements": [], "prompt": "

Find $L\\{\\var{a}+\\var{b}t \\}$.

", "expectedvariablenames": [], "checkingaccuracy": 0.001, "type": "jme", "showpreview": true, "vsetrangepoints": 5, "variableReplacementStrategy": "originalfirst", "steps": [{"prompt": "

$L\\{k\\}=\\frac{k}{s}$

\n

$L\\{t\\}=\\frac{1}{s^2}$

", "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "showCorrectAnswer": true, "scripts": {}, "marks": 0, "type": "information"}], "marks": 1, "scripts": {}, "answer": "{a}/s+{b}/s^2", "showCorrectAnswer": true, "checkvariablenames": false, "checkingtype": "absdiff", "vsetrange": [0, 1]}, {"stepsPenalty": 0, "variableReplacements": [], "prompt": "

Find $L\\{t^\\var{a}\\}$.

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$L\\{t^n\\}=\\frac{n!}{s^{n+1}}$

", "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "showCorrectAnswer": true, "scripts": {}, "marks": 0, "type": "information"}], "marks": 1, "scripts": {}, "answer": "fact({a})/s^{a+1}", "showCorrectAnswer": true, "checkvariablenames": false, "checkingtype": "absdiff", "vsetrange": [0, 1]}, {"stepsPenalty": 0, "variableReplacements": [], "prompt": "

Find $L\\{\\var{a}t^\\var{c}+\\var{b}t^\\var{d}\\}$.

", "expectedvariablenames": [], "checkingaccuracy": 0.001, "type": "jme", "showpreview": true, "vsetrangepoints": 5, "variableReplacementStrategy": "originalfirst", "steps": [{"prompt": "

$L\\{t^n\\}=\\frac{n!}{s^{n+1}}$

", "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "showCorrectAnswer": true, "scripts": {}, "marks": 0, "type": "information"}], "marks": 1, "scripts": {}, "answer": "({a}*(fact({c})))/s^{c+1}+({b}*(fact({d})))/s^{d+1}", "showCorrectAnswer": true, "checkvariablenames": false, "checkingtype": "absdiff", "vsetrange": [0, 1]}], "statement": "

You may use a table of Laplace transforms in order to answer the following questions.

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Laplace of constants and powers of t

\n

rebelmaths

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(a) Using the tables,  $L[e^{\\var{a}t}]=\\frac{1}{s-\\var{a}}$

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(b) Using the tables,  $L[e^{\\var{b}t}]=\\frac{1}{s-(\\var{b})}$

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(c) Using the tables,  $L[e^{\\var{c}t}+e^{\\var{d}t}]=\\frac{1}{s-(\\var{c})}+\\frac{1}{s-\\var{d}}$

", "rulesets": {}, "parts": [{"stepsPenalty": 0, "vsetrangepoints": 5, "prompt": "

Find the laplace transform of $e^{\\var{a}t}$

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Note that the Laplace transform of $e^{at}$ is $\\frac{1}{s-a}$

\n

$L\\{e^{at}\\}=\\frac{1}{s-a}$

", "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "showCorrectAnswer": true, "scripts": {}, "marks": 0, "type": "information"}], "showCorrectAnswer": true, "scripts": {}, "answer": "1/(s-{a})", "marks": 1, "checkvariablenames": false, "checkingtype": "absdiff", "type": "jme"}, {"stepsPenalty": 0, "vsetrangepoints": 5, "prompt": "

Find the laplace transform of $e^{\\var{b}t}$

", "expectedvariablenames": [], "checkingaccuracy": 0.001, "vsetrange": [0, 1], "showpreview": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "steps": [{"prompt": "

Note that the Laplace transform of $e^{at}$ is $\\frac{1}{s-a}$

\n

$L\\{e^{at}\\}=\\frac{1}{s-a}$

", "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "showCorrectAnswer": true, "scripts": {}, "marks": 0, "type": "information"}], "showCorrectAnswer": true, "scripts": {}, "answer": "1/(s-{b})", "marks": 1, "checkvariablenames": false, "checkingtype": "absdiff", "type": "jme"}, {"stepsPenalty": 0, "vsetrangepoints": 5, "prompt": "

Find the laplace transform of $ { e^{ \\var{c} t}+e^{ \\var{d} t} }$

\n

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When you have the Laplace transform of two functions added together you just get the Laplace transform of each function and add the two answers.

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$L\\{f(t)+g(t)\\}=L\\{f(t)\\}+L\\{g(t)\\}$

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You may use a table of Laplace transforms in order to answer the following questions.

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Laplace transform of e^{at}

\n

rebelmaths

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See 'show steps'.

", "rulesets": {}, "parts": [{"stepsPenalty": 0, "variableReplacements": [], "prompt": "

Find $L\\{\\cos(\\var{a}t)\\}$

\n

", "expectedvariablenames": [], "checkingaccuracy": 0.001, "type": "jme", "showpreview": true, "vsetrangepoints": 5, "variableReplacementStrategy": "originalfirst", "steps": [{"prompt": "

Note: $L\\{\\cos(bt)\\}=\\frac{s}{s^2+b^2}$

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In this example $b=\\var{a}$

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Find $L\\{\\sin(\\var{b}t)\\}$

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Note: $L\\{\\sin(bt)\\}=\\frac{b}{s^2+b^2}$

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In this example $b=\\var{b}$

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Find $L\\{\\cos(\\frac{t}{\\var{a}})+\\sin(\\frac{t}{\\var{b}})\\}$

\n

", "expectedvariablenames": [], "checkingaccuracy": 0.001, "type": "jme", "showpreview": true, "vsetrangepoints": 5, "variableReplacementStrategy": "originalfirst", "steps": [{"prompt": "

Note: $L\\{\\cos(bt)\\}=\\frac{s}{s^2+b^2}$ and  $L\\{\\sin(bt)\\}=\\frac{b}{s^2+b^2}$

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In the first part $b=\\frac{1}{\\var{a}}$ and in the second part $b=\\frac{1}{\\var{b}}$

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You may use a table of Laplace transforms in order to answer the following questions.

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rebelmaths

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Time is up - you must start the test again.

"}, "timedwarning": {"action": "warn", "message": "

You have 5 minutes to complete the test.

"}}, "feedback": {"showactualmark": true, "showtotalmark": true, "showanswerstate": true, "allowrevealanswer": true, "advicethreshold": 0, "intro": "

This test is on simple Laplace transforms. It will reward those of you who have attended and completed Journal 3 with an easy 3% for this module. For those of you who have not attended and are a little behind, this test should hopefully help you grasp the basics now and earn you 3% whilst doing it.

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You have 30 minutes to complete this test. You may pause it, and you may reveal answers for help and regenerate another question to attempt.

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As usual once you have scored full marks DO NOT ENTER the test again as this will wipe your grade.

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