JEE MAIN - Physics (2021 - 27th July Morning Shift - No. 5)
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 9 m/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 :
_27th_July_Morning_Shift_en_5_1.png)
6 m/s
9 m/s
4 m/s
3 m/s
Explanation
Collision between A and B
_27th_July_Morning_Shift_en_5_2.png)
m $$\times$$ 9 = mv1 + 2mv2 (from momentum conservation)
$$e = 1 = {{{v_2} - {v_1}} \over 9}$$
$$\Rightarrow$$ v2 = 6 m/sec. v1 = $$-$$3 m/sec.
collision between B and C
_27th_July_Morning_Shift_en_5_3.png)
2m $$\times$$ 6 = 4mv (from momentum conservation)
v = 3 m/s
m $$\times$$ 9 = mv1 + 2mv2 (from momentum conservation)
$$e = 1 = {{{v_2} - {v_1}} \over 9}$$
$$\Rightarrow$$ v2 = 6 m/sec. v1 = $$-$$3 m/sec.
collision between B and C
2m $$\times$$ 6 = 4mv (from momentum conservation)
v = 3 m/s
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