Three objects A, B and C are kept in a straight line on a frictionless horizontal surface. The masses of A, B and C are m, 2m and 2m respectively. A moves towards B with a speed of 9m/s and makes an elastic collision with it. Thereafter B makes a completely inelastic collision with C. All motions occur along same straight line. The final speed of C is:

Option 1 -

4 m/s

Option 2 -

6 m/s

Option 3 -

9 m/s

Option 4 -

3 m/s

2 Views | Posted a month ago

Asked by Shiksha User

1 Answer

Answered by

Vishal Baghel | Contributor-Level 10

a month ago

Correct Option - 4

Detailed Solution:

Let vel of A and B just after collision be VA & VB respectively.
m × 9 + 0 = m × VA + 2mVB
9 = VA + 2VB
again e = (VB - VA)/ (9-0) = 1
9 = VB - VA
From (i) & (ii)
VB = 6 m/s & VA = -3 m/s
Now, for B and C collision (completely inelastic):
2m × 6 + 0 = (2m + 2m)Vc
12m = 4mVc
Vc = 3 m/s

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