[5] For perfectly elastic, one dimensional collisions in the center of mass fram

Question

[5] For perfectly elastic, one dimensional collisions in the center of mass frame, the final velocities of the two objects are equal to
a) the negative of the initial velocities because the center of mass must remain stationary. b) the initial velocity of the other mass because they exchange motions.

c) the negative of the initial velocities because the kinetic energy of each must be constant.

d) negative the initial velocity of the other mass because they exchange motion and change direction.
e) none of these.

[6] Two disks of radius 2 cm. collide elastically and off-center. The final velocity components which are perpendicular to the line between centers at contact are

a) equal to negative their initial values. b) the same as before collision.

c) equal to the initial component of the other disk. d) zero. _______________________________________________________________________

[7] Two carts of equal mass move on a frictionless track. The red cart is initially at rest and the blue cart approaches it at 0.25 m/s. The velocity of the red cart after a perfectly elastic collision is how many times as large as the velocity after a totally inelastic collision (with data as above)?

(a) 12 (b) 1 (c) 2 (d) 0

Explanation / Answer

5. d) negative the initial velocity of the other mass because they exchange motion and change direction.

6. c) equal to the initial component of the other disk.

7. in elastic collision

       v = 0.25 m/s

in inelastic collision

v = (0.25/2 ) m/s

(c) 2

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