Uppgift 3.4: 10, 11. Bojen. 

Typesetting:-mrow(Typesetting:-mi( 

Uppgift 10 

"Bojekvationen" blir om ρ betecknar vatnets och ϱ bojens densiteter 

Typesetting:-mrow(Typesetting:-mi( 

`*`(`ϱ`, `*`(h, `*`(Pi, `*`(`^`(r, 2), `*`(((`@@`(D, 2))(x))(t)))))) = `+`(`*`(`ϱ`, `*`(g, `*`(h, `*`(Pi, `*`(`^`(r, 2)))))), `-`(`*`(rho, `*`(g, `*`(x(t), `*`(Pi, `*`(`^`(r, 2)))))))) (4.1)
 

Begynnelsedata. 

Typesetting:-mrow(Typesetting:-mi( 

x(0) = 0, (D(x))(0) = 0 (4.2)
 

Lösningen. 

Typesetting:-mrow(Typesetting:-mi( 

x(t) = `+`(`-`(`/`(`*`(cos(`/`(`*`(`^`(rho, `/`(1, 2)), `*`(`^`(g, `/`(1, 2)), `*`(t))), `*`(`^`(`ϱ`, `/`(1, 2)), `*`(`^`(h, `/`(1, 2)))))), `*`(`ϱ`, `*`(h))), `*`(rho))), `/`(`*`(`&varr... (4.3)
 

De givna numeriska värdena i uppgift 10 i cm, gram och sek (cgs-enheter). 

Typesetting:-mrow(Typesetting:-mi( 

{rho = 1, `ϱ` = .5, h = 200.0, g = 980.0} (4.4)
 

ger lösningen 

Typesetting:-mrow(Typesetting:-mi( 

x(t) = `+`(`-`(`*`(100.00, `*`(cos(`+`(`*`(3.130495168, `*`(t))))))), 100.00) (4.5)
 

Typesetting:-mrow(Typesetting:-mi( 

proc (t) options operator, arrow; `+`(`-`(`*`(100.00, `*`(cos(`+`(`*`(3.130495168, `*`(t))))))), 100.00) end proc (4.6)
 

som ser ut sÃ¥ här 

Typesetting:-mrow(Typesetting:-mi( 

Plot_2d
 

och periodtiden blir 

Typesetting:-mrow(Typesetting:-mi( 

`+`(`/`(`*`(2, `*`(Pi, `*`(`^`(`ϱ`, `/`(1, 2)), `*`(`^`(h, `/`(1, 2)))))), `*`(`^`(rho, `/`(1, 2)), `*`(`^`(g, `/`(1, 2)))))) (4.7)
 

Typesetting:-mrow(Typesetting:-mi( 

`+`(`*`(.6388765650, `*`(Pi))) (4.8)
 

Typesetting:-mrow(Typesetting:-mi( 

2.007089923 (4.9)
 

Uppgift 11 

Typesetting:-mrow(Typesetting:-mi( 

Givna data konverteras till cgs-enheter genom att använda funktionen convert 

Typesetting:-mrow(Typesetting:-mi( 

{rho = 1, g = 980.0, p = 2.500000000, m = 45359.23700} (4.10)
 

Med Typesetting:-mrow(Typesetting:-mi( fÃ¥r vi ekvationerna 

Typesetting:-mrow(Typesetting:-mi( 

{m = `*`(a, `*`(Pi, `*`(`^`(r, 2)))), `+`(`/`(`*`(2, `*`(Pi)), `*`(p))) = `/`(`*`(`^`(rho, `/`(1, 2)), `*`(`^`(g, `/`(1, 2)))), `*`(`^`(a, `/`(1, 2))))} (4.11)
 

som med ovanstÃ¥ende data blir 

Typesetting:-mrow(Typesetting:-mi( 

{45359.23700 = `*`(a, `*`(Pi, `*`(`^`(r, 2)))), `+`(`*`(.8000000000, `*`(Pi))) = `+`(`/`(`*`(31.30495168), `*`(`^`(a, `/`(1, 2)))))} (4.12)
 

och som har lösningarna 

Typesetting:-mrow(Typesetting:-mi( 

[[a = 155.1480624, r = 9.646832900], [a = 155.1480624, r = -9.646832900]] (4.13)
 

där den positiva lösningen ger Typesetting:-mrow(Typesetting:-mi(  i cm. 

Typesetting:-mrow(Typesetting:-mi( 

9.646832900 (4.14)
 

För att fÃ¥ svaret i tum konverterar vi igen 

Typesetting:-mrow(Typesetting:-mi( 

3.797965709 (4.15)