Question

compute the power required by a man to move a 10kg mass so as to change the speed of mass from 10m/s and 20m/s.

Answer 1

Solutions 

Mass, m = 10 kg 
Initial velocity, u = 10 m / s
Final velocity, v = 20 m / s 
⇒ 1 / 2 x m x [v²-u²]

Calculations

1 / 2 x 10 x [(20)²-(10)²]
= 5 x (400 - 100)
= 5 x 300 
 = 1500 J

Power, P = Work done / Time consumed 

 = 1500 J / 5 s
  = 300 J / s or W

Hence, the power required by a man to move a 10 kg mass so as to change the speed of mass from 10 m / s to 20 m / s in 5 seconds is 300 J / s or W.