A) 600 J
B) 800 J
C) 1000J
D) 1200J
Correct Answer: B
Solution :
Given, \[{{m}_{1}}=20kg,{{u}_{1}}=10m/s,\] Using law of conservation of momentum, \[{{m}_{1}}{{u}_{1}}+{{m}_{2}}{{u}_{2}}=({{m}_{1}}+{{m}_{2}})v\] \[20\times 10+5\times 0=(20+5)\times v\] \[\therefore \] \[v=\frac{200}{25}=8m/s\] Kinetic energy of the composite mass \[=\frac{1}{2}({{m}_{1}}+{{m}_{2}}){{v}^{2}}\] \[=\frac{1}{2}(20+5)\times {{(8)}^{2}}=25\times 32=800J\]You need to login to perform this action.
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