Oefenopgaven hoofdstuk 5 uitwerkingen 1a. (3) W = F ⋅ s (1) = 75 ⋅ 50∙103 (1) = 3.8⋅106 J (1) 1b. (3) v = Pm / Fv (1) = 2000 / 75 (1) = 27 m/s (1) 1c. (3) 40% = 3.75∙106 J (antwoord a) (1) 60% is verloren gegaan. Dat is 1.5 keer (1) zoveel dus 5.6∙106 J (1) Totaal vraag 1: 9 2a. (4) WFz = - Fz ∙ h (1) = - 120 ∙ 9.81 (1) ∙ 170 ∙ sin 18° (1) = - 6.2∙104 J (1) 2b. (2) 60 = 35 + 0.62∙v2(1) v = 6.4 m/s (1) 2c. (4) v = 12 / 3.6 = 3.3 m/s (1) Fw = 35 + 0.62⋅(3.3)2 = 42 N (1) WFw = - Fw ∙ s (1) = - 42 ∙ 170 = -7121 = -7.1∙103 J (1) 2d. (5) WFv = WFw + WFz (1) = 7.1∙103 + 6.2∙104 = 6.9∙104 J (1) Fv = WFv / s = 6.9∙104 / 170 = 406 N (1) Pm = Fv ∙ v = 406 ∙ 3.3 (1) = 1.4∙103 W (1) Totaal vraag 2: 15 3a. (2) E = 15∙10-3 ∙ 16.5∙106 (1) = 247500 = 2.5∙105 J (1) 3b. (4) η = W / Ech = 0.05 (1) W = 247500 ∙ 0.05 = 12375 J nuttige arbeid uit 1 ijsje (1) Een dag op de beurs kost W = F ∙ s = 25 ∙ 3.5∙103 = 87500 J (1) Dat zijn dus 87500 / 12375 = 7 ijsjes (1) Totaal vraag 3: 6