A bullet of mass 20 g has speed 1 m s⁻¹ just before entering a mud wall 20 cm thick. The wall offers mean resistance 2.5×10⁻² N. The speed after emerging is closest to:
Options

Question

A bullet of mass 20 g has speed 1 m s⁻¹ just before entering a mud wall 20 cm thick. The wall offers mean resistance 2.5×10⁻² N. The speed after emerging is closest to:

G1 Physics · Accepted Answer

Initial kinetic energy=(1/2)(0.02)(1²)=0.01 J. Work done against resistance=(2.5×10⁻²)(0.20)=0.005 J. Final KE=0.005 J=(1/2)(0.02)v², giving v²=0.5 and v≈0.707 m s⁻¹. Hence option D.