A boy is paddling bicycle it is moving with the speed of 7 m/s suddenly breaks applied speed reduces to 2 m/s find the work of break done on bicycle

Question

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Answer 1

As Michael C. suggested, there is not sufficient information to fully answer the question.  The work done is the change in kinetic energy, but without knowing the mass of the boy+bicycle, we can at best give you the work done per unit mass.

 

K = kinetic energy = (1/2)mv²

 

W = work = ΔK = K_f - K_i = (m/2)(v_f² - v_i²) = (m/2)[(2² - 7²) (m/s)²]

 

W = -(m/2)(45 m²/s²)

 

w = work per unit mass = W/m = -(45/2) m²/s² = -22.5 m²/s²

 

The negative sign means the braking force was applied against the direction of motion.