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Question Number 81011 by mr W last updated on 08/Feb/20

Commented by mr W last updated on 08/Feb/20

A ball with mass m and radius r falls  from a height of h and hits two wedges  with mass M for each as shown.  If the coefficient of restitution is e  and the friction coefficient between  wedges and ground is μ, find the  distance the wedges move.

AballwithmassmandradiusrfallsfromaheightofhandhitstwowedgeswithmassMforeachasshown.Ifthecoefficientofrestitutioniseandthefrictioncoefficientbetweenwedgesandgroundisμ,findthedistancethewedgesmove.

Commented by ajfour last updated on 09/Feb/20

Commented by ajfour last updated on 09/Feb/20

u=(√(2g(h−rsec α)))     ....(i)  Vsin α+vcos α= eucos α   ..(ii)  Jsin α=sin α∫Ndt=MV  ;    2Jcos α=m(v+u)  ⇒  2MVcos α=m(v+u)sin α  using (ii):  2MVcos^2 α=m{eucos α−Vsin α                              +ucos α}sin α  V=((mu(e+1)cos αsin α)/(2Mcos^2 α+msin^2 α))  2μMgL=MV^(  2)   ⇒  L=(V^(  2) /(2μg))  L=(u^2 /(2μg)){((m(e+1)cos αsin α)/(2Mcos^2 α+msin^2 α))}^2    L=(((h−rsec α))/μ){(((e+1)tan α)/(((2M)/m)+tan^2 α))}^2  .

u=2g(hrsecα)....(i)Vsinα+vcosα=eucosα..(ii)Jsinα=sinαNdt=MV;2Jcosα=m(v+u)2MVcosα=m(v+u)sinαusing(ii):2MVcos2α=m{eucosαVsinα+ucosα}sinαV=mu(e+1)cosαsinα2Mcos2α+msin2α2μMgL=MV2L=V22μgL=u22μg{m(e+1)cosαsinα2Mcos2α+msin2α}2L=(hrsecα)μ{(e+1)tanα2Mm+tan2α}2.

Commented by mr W last updated on 09/Feb/20

thanks alot sir!  why is the momentum conservation  in vertical direction not appliable?

thanksalotsir!whyisthemomentumconservationinverticaldirectionnotappliable?

Commented by ajfour last updated on 09/Feb/20

while collision takes place,  normal reaction from ground  on wedges, increases substan-  cially and back to Mg.

whilecollisiontakesplace,normalreactionfromgroundonwedges,increasessubstanciallyandbacktoMg.

Commented by mr W last updated on 09/Feb/20

that′s it!

thatsit!

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