Question

Five spheres of masses 1, 2, 3, 4 and 5 kg are moving along a straight line in the same direction with velocities 5, 4, 3, 2 and 1 m/s respectively. The first sphere collides with the second and both stick together. The compound mass collides with the third sphere and so on. The velocity of the compound mass when all spheres stick together is

• A. $\frac{3}{7}$ m/s
• B. $\frac{7}{3}$ m/s
• C. $1$ m/s
• D. none of the above

Answer 1

The correct option is B $\frac{7}{3}$ m/s

Using momentum conservation,

$5\times 1+4\times 2+3\times 3+4\times 2+1\times 5=15\times v$

$5+8+9+8+5=15\times v$

$35=15\times v$

$v=\frac{7}{3}m/s$