d) You are given two carts A, B. They look outwardly identical but you don\'t kn

Question

d) You are given two carts A, B. They look outwardly identical but you don't know which weighs more. You place A at rest on an air track and give B an initial velocity to the right so it collides elastically with A. After the collision both cars move to the right, the velocity of B being smaller than before the collision. What do you conclude? as ca the two carts are identical cart B has less mass than cart A need more information to conclude anything about the masses of the carts e) Two objects collide totally inelastically. Can all the kinetic energy in the collision be converted to other forms of energy? yes, all kinetic energy is converted to other energies whenever the objects stick together no, this violates a fundamental law of physics none of the above

Explanation / Answer

d)

We use below formulae for elastic collision,

v1f = [(m1-m2)/(m1+m2)]v1i + [(2m2)/(m1+m2)]v2i --------------(1)

v2f = [(2m1)/(m1+m2)]v1i + [(m2-m1)/(m1+m2)]v2i -----------(2)

Condition given are v2f < v2i , v1f > v1i and v1i = 0

Put m1=m2 => v2f = v1i ---------------which is not valid to the conditions given, hence incorrect.

Put m1>m2 => v2f > v1i ---------------which is not valid to the conditions given, hence incorrect.

Put m1<m2 => v2f < v1i ---------------which is valid to the conditions given, hence correct.

e)

For inelastic collision KE is not conserved. But after collision both objects have positive velocities

So we can write,

KE = KEf - KEi = Positive values,

Or

KEf > KEi

KE is the lost energy during the collision.

However law of conservation of energy states that no energy can be created or destroyed.

Hence one can say that lost energy KE is converted into other forms of energies such as thermal heat, sound , friction etc.

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