Question

A bullet of mass $10g$ leaves a rifle at an initial velocity of $1000m/s$ and strikes the earth at the same level with a velocity of $500m/s$. the work done in joules overcoming the resistance of air will be

• A. $375$
  
• B. $3750$
  
• C. $500$
  
• D. $5000$
  

Answer 1

Answer: (B)

$3750$

By work energy theorem

Work done in overcoming the air resistance=Loss in energy

Initial KE=$0.5\times m\times v_1^2=0.5\times 0.01\times {10}^6=5000J$

Final KE=$0.5\times m\times v_2^2=0.5\times 0.01\times 25\times {10}^4=1250J$

$\Rightarrow$Work done in overcoming the air resistance$=5000-1250=3750J$

Hence correct answer is option $B$