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Question Number 155034 by peter frank last updated on 24/Sep/21

Commented by peter frank last updated on 24/Sep/21

i think h_o =l  u_o =max speed

ithinkho=luo=maxspeed

Commented by mr W last updated on 24/Sep/21

please check your typos!  what is h_0 ?, what is u_0 ?, maximum  speed or minimum speed?

pleasecheckyourtypos!whatish0?,whatisu0?,maximumspeedorminimumspeed?

Commented by mr W last updated on 24/Sep/21

no. that is the minimum speed the  bullet must have. if the speed is less  than it, the bob can not complete a  circle.

no.thatistheminimumspeedthebulletmusthave.ifthespeedislessthanit,thebobcannotcompleteacircle.

Commented by mr W last updated on 24/Sep/21

and it should be u_0 =((4m)/m_0 )(√(5gl)) , not   u_0 =((4m_0 )/m)(√(5gl)) .

anditshouldbeu0=4mm05gl,notu0=4m0m5gl.

Answered by mr W last updated on 24/Sep/21

from Q154851:  v_0 ^2 ≥5gl  m_0 u_0 =mv_0 +m_0 ((3u_0 )/4)  u_0 =((4m)/m_0 )×v_0 ≥((4m)/m_0 )(√(5gl))

fromQ154851:v025glm0u0=mv0+m03u04u0=4mm0×v04mm05gl

Answered by peter frank last updated on 25/Sep/21

Commented by peter frank last updated on 25/Sep/21

before collision

beforecollision

Answered by peter frank last updated on 25/Sep/21

Commented by peter frank last updated on 25/Sep/21

after collision

aftercollision

Commented by peter frank last updated on 25/Sep/21

since there are collision,  momentum is conserved  Momentum before collisio(M_(bc) )=  Momentum after  collision(M_(apc) )=  u_o m_o +m_B u_B =(3/4)m_o u_o +Mv_B   u_B =0  v_B =((m_o u_o )/(4M))   ...(i)  Total Energy at the bottom=  Total Energy at the Top(highest)  E_B =E_T   K.E_B +P.E_B =K.E_H +P.E_H   (1/2)Mv_o ^2 +mg(0)=(1/2)Mv_H ^2 +mg(l+l)  v_B ^2 =v_H ^2 +4gl  ....(ii)  (((m_o u_o )/(4M)) )^2 =V_H ^2 +4gl  v_H ^2 =((m_o ^2 u_o ^2 )/(16M))  −4gl   .....(iii)  for any particle to complete a  circle safely  ((mv_H ^2 )/r)>mg  (v_H ^2 /r)>g  v_H ^2 >gr   .....(iv)  ((m_o ^2 u_o ^2 )/(16M))  −4gl >gr [r=l]  ((m_o ^2 u_o ^2 )/(16M)) >5gl  m_o ^2 u_o ^2 >80Mgl  u_o >((√(80Mgl))/m_o )  u_o >((4M(√(5gl)))/m_o )  u_o =((4M(√(5gl)))/m_o )

sincetherearecollision,momentumisconservedMomentumbeforecollisio(Mbc)=Momentumaftercollision(Mapc)=uomo+mBuB=34mouo+MvBuB=0vB=mouo4M...(i)TotalEnergyatthebottom=TotalEnergyattheTop(highest)EB=ETK.EB+P.EB=K.EH+P.EH12Mvo2+mg(0)=12MvH2+mg(l+l)vB2=vH2+4gl....(ii)(mouo4M)2=VH2+4glvH2=mo2uo216M4gl.....(iii)foranyparticletocompleteacirclesafelymvH2r>mgvH2r>gvH2>gr.....(iv)mo2uo216M4gl>gr[r=l]mo2uo216M>5glmo2uo2>80Mgluo>80Mglmouo>4M5glmouo=4M5glmo

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