1.

A running man has half the kinetic energythat a boy of half his mass 'has. The manspeeds up by 1.0 meter/sec and then hasthe same kinetic energy as the boy. Whatwere the original speeds of man and boy ?(A) 2.4 m/sec, 4.8m/sec(B) 4.8m/sec, 2.4m/sec(C) 4.2 m/sec, 8.4m/sec(D) 8.4m/sec, 4.2m/sec

Answer»

Mass of man= mmass of boy= 1/2 mspeeds= v1 and v2KE of man= 1/2 mv1²KE of boy= 1/2 (m/2)v2²comparing both equtions1/2mv1²= 1/2 (m/2)v2²v1²= 1/4v2²

new speed = (v1+1)New KE:1/2 m(v1+1) = 1/2 (m/1)v2²(v1+1)²= 1/2 v2²

By putting the values in both equations we get:v1= 2.41m/sv2= 4.82 m/s



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