Q19 of 55 Page 361

A block of mass 5 Kg is lying on a frictionless table. A force of 20 N is applied on it for 10 seconds. Calculate its kinetic energy.

Given,

Mass of body = 5 kg


Force F = 20 N


Time t = 10 seconds


To find: kinetic energy??


Initial velocity u = 0


Let final velocity be v


We know,



So, acceleration = 4 ms-2


We also know that,



Substituting value of acceleration and u in this formula:



v = 10 s × 4 ms-2


v = 40 ms-1


Kinetic energy = m v2


Substituting value of v in the equation


Kinetic energy =


= 4000 J


= 4 KJ


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