07prob_11

07prob_11 - Assigment #7, 5/13/11 Page 1 of 4 UC Davis...

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Unformatted text preview: Assigment #7, 5/13/11 Page 1 of 4 UC Davis Physics 9A-C Assignment #7 Cole [8.7] p t = 0.045 kg ( ) 25 m ( ) 2 10 3 s =563N.TheweightoftheballislessthanhalfaNewton,sothe weightisnotsignificantwhiletheballandclubareincontact. [8.20]a)Thisprocesshappensinthecenterofmassframewhere p= 0,bothbeforeandafter thecollision. m A v A + m B v B = . v A = m B v B m A = 3 kg 1 kg 1.2 m/s ( ) =-3.6m/s b)Thisisaninelastic"explosion",butitusespotentialenergystoredinthespringsowecan conservetotalenergy, E=E f .Thepotentialenergyofthespringappearsaskineticenergyof themasses: U=K A +K B = (1/2)(1.00kg)(3.60m/s) 2 +(1/2)(3.00kg)(1.200m/s) 2 =8.64J . [8.27]Astherainhitsthecar,thewaterexperiencesanimpulseinthedirectionoftravelofthe carwhichspeedsthewaterupsoittravelshorizontallywiththecar,andthecarexperiencesand equalbutoppositeimpulsewhichslowsthecardown.Conservingmomentum Mv=(m+M)v v = 2.4 10 4 kg 4 m/s ( ) 2.7 10 4 kg = 3.56m/s. [8.35]a)Thesmallcarplacesaforce F onthelargecar,andbyNewton's3rdlaw,thelargecar mustplaceanequalbutoppositeforceonthesmallcar. F = p t Theyexperienceequalbut oppositemomentumchanges. m s v s = m L v L v s = m L m s v L = 3000 1200 v L = 2.5 v L b)Theaccelerationisproportionaltothevelocitychange;hence,thesmallcarhas2.5timesthe accelerationofthelargecar.Theforcesexperiencedbythesmallcarpassengersare2.5times thatofthelargecar.Thisdifferencecanbemitigatedbybuildingcrumplezonesintocarssothe anypassengerswearingseatbeltsstopmoreslowly.However,notethatmassivecarshaveabig safetyadvantagejustbyvirtueoftheirlargemass. [8.37]Theinitialmomentumofthecarmustbethe x-componentofthefinalmomentum asthetruckhadnoinitial x-componentofmomentum,so p x =m car v car =(m car +m truck )v sin24 v car = m car + m truck ( ) m car v sin24 = 2850 950 16 m/s ( ) sin24 =19.5m/s. Forthe y- direction: p y...
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07prob_11 - Assigment #7, 5/13/11 Page 1 of 4 UC Davis...

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