question_answer

A body dropped from a height 'h' with an initial speed zero, strikes the ground with, a velocity 3 km/ h. Another body of same mass dropped from the same height 'h' with an initial speed 4 km/h. Find the final velocity of second mass, with which it strikes the ground.

Answer:

1st body: \[a=g,\,\,u=0,\,\,v=3km/h\] distance travelled = h using \[{{v}^{2}}-{{u}^{2}}=2as\] we have\[{{3}^{2}}=2gh\Rightarrow 2gh=9\]                      ??????(1) 2nd body: \[a=g,\,\,u=4km/h.\] distance travelled\[=h,\,\,v=?\] using\[{{v}^{2}}-{{u}^{2}}=2as\Rightarrow {{v}^{2}}-41=2gh\]     ??????(2) In both the cases the height and mass are same. \[\Rightarrow {{v}^{2}}-{{4}^{2}}={{3}^{2}}\] \[\Rightarrow {{v}^{2}}-{{4}^{2}}+{{3}^{2}}=16+9=25\] \[\therefore \,\,\,v=5km/h\]