are l 78418924 2048 Spring 2016 2 ercise 847 incorrect Try Again 5 attempts rema

Question

are l 78418924 2048 Spring 2016 2 ercise 847 incorrect Try Again 5 attempts remaining locks A (mass 400 kg) and Bilmass 900 on a horizonta InMaly, block Bis al rest and block A Part C toward a 300 m/s The blocks are equpped with ideal The collision is headon soal motion before and after the Find the velocity of block B when the energy stored in the spring bumpers is maxi motion of along straignline Let be the drettion of the intial block A Express your answer with the appropriate units. Value T Units Submit Incorrect. Try Again: 5 attempts remaining Part D Find the velocity of A after they have moved apart block your answer with the ni My Answers ome velocity of answer with the

Explanation / Answer

Applying the law of conservation of energy to the system of colliding blocks,we have,

K+U= constant where K is the kinetic energy and U is the potential energy.

Just before block A collides with B,

K=1/2*mA*uA2=1/2*4*9=18 J

Since the energy stored in the spring bumpers is maximum, all the initial k.e of the block A is converted into p.e.

Thus U=K=18 J.

Therefore we have K+U=36=1/2*mA*vA2+1/2*mB*vB2 where vA and vB are the final velocities of blocks A and B respectively.

i.e. 36=2vA 2+9/2 vB2 eq. 1

Also from the law of conservation of linear momentum we have

mA uA +0=mAvA +mBvB

i.e. vA=3- 9/4vB   eq.2

Substituting this value of vA in eq. 1 we obtain a quadratic equation in vB which on solving yields the values of vA and vB as -2.2 m/s and 2.3 m/s respectively.

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