P112Sol7S06 - 6-34[Leg Presses](a) First, find the spring...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 6-34[Leg Presses](a) First, find the spring constant k:Wby you= - Wby spring= 12kx2- 0 ⇒k = 2Wby springx2= 2(80.0 J)(0.200 m)2= 4000 N/mNow, the force: F = kx = (4000 N/m)(0.200 m) = 800 N(b) Wby you= - Wby spring= 12kxf2- 12kxo2= 12k(xf2- xo2)= 12(4000 N/m) [(0.400 m)2- (0.200 m)2] = 240 J7-12[Tarzan and Jane]Take y = 0 to be at the bottom of Tarzan's swing. Hestarts at height yo= L - L cos45° and descends to finalheight yf= L - L cos30°.Use Cons. of Energy to find Tarzan's final speed:Ko+ Ugo= Kf+ Ugf0 + mgyo= 12mvf2+ mgyfSolve for vf= 2g(yo- yf) = 2gL(cos30° - cos45°)= 2(9.8 m/s2)(20.0 m)(0.866 - 0.707) = 7.9 m/sThis is pretty fast. Tarzan knocks Jane off her feet like a football player making a tackle. Ahh-ee-aahhh!!!7-24[Satellite Launcher](a)The maximum acceleration occurs when the net force on the satellite is maximum. This iswhen the spring is fully compressed.Applying N’s 2ndLaw:Fmax= k xmax= m amax(1)When the satellite is going at its maximum speed, all of the PE initially stored in the spring has beenconverted to KE of the satellite:_ k xmax2= _ m vmax2(2)Using Equs (1) and (2), we can find both k and xmax....
View Full Document

This homework help was uploaded on 04/21/2008 for the course PHYS 1112 taught by Professor Leclair,a during the Fall '07 term at Cornell University (Engineering School).

Page1 / 4

P112Sol7S06 - 6-34[Leg Presses](a) First, find the spring...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online