Question

Calculate the work done when an object of mass 100 kg changes its velocity from 40km/h to 20km/h

Answer 1

Explanation:

according to work-energy theorem,

W=∆K=K(final)–K(initial)

$= \frac{1}{2} m {v}^{2} - \frac{1}{2} m {u}^{2} \\ = \frac{1}{2} 100kg \times( 20 \times \frac{5}{18} )m {s}^{ - 1} - \frac{1}{2} 100kg \times( 40 \times \frac{5}{18} )m {s}^{ - 1} \\ = 50 \times \frac{50}{9} - 50 \times \frac{100}{9} \\ = \frac{2500 - 5000}{9} \\ = \frac{ - 2500}{9}$