Question

A mass of 1 kg is thrown up with a velocity of 100 m/s. After 5 seconds, it explodes into two parts. One part of mass 400 g comes down with a velocity 25 m/s, Calculate the velocity of other part:

• A. $40\ m/s \ upward$
• B. $40 \ m/s\ downward$
• C. $100\ m/s \ upward$
• D. $60\ m/s\ upward$

Answer 1

Answer: (C)

$100\ m/s \ upward$

Answer 2

$Velocity\ after \ 5 \ second$

$v=100–10×5$

$v = 50 \ m/s.$

$from\ conservation \ of \ momentum$

$1×50\hat j=0.4×25(-\hat j)+0.6\vec v$

$50\hat j+10\hat j=0.6\vec v$

$\vec v=\frac {60\hat j }{0.6} =100\hat j=100\ m/s\ \hat j$

$So, \ the\ correct\ option\ is \ (C):$ $100\ m/s \ upward$