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Lakhmir Singh Solutions Class 9 Physics Solutions for Exercise in Chapter 4 - Work And Energy

Question 33 Exercise

A body of 2 kg falls from rest. What will be its kinetic energy during the fall at the end of 2s?

Answer:

Mass of body = 2 kg

Initial velocity, u = 0

Time taken, t = 2 s

Acceleration due to gravity, g = 10 m/s2

Final velocity, v = ?

Using the first equation of motion,

v = u + gt = 20 m/s

KE = \frac{1}{2}mv^2 = 400 J [

Video transcript
"hey kids welcome to lido q a video i am vinit your leader tutor bringing you this question on your screen a body of 2 kg falls from rest what will be its kinetic energy during the fall at the end of two seconds here the time is given to you the mass is given to you initial velocity is zero for kinetic energy we need the final velocity but we don't have it so let us find it so what is given to you u is equal to 0 meter per second mass is 2 kg time is equal to 2 second and g we know is 9.8 meter per second square now we know u sorry v is equal to u plus gt this implies v is equal to u 0 plus 9.8 into 2 this implies v is equal to 19.6 meter per second right now let us find the kinetic energy of the body now that we have v so kinetic energy is equal to half mv square that is equal to half into mass is 2 kg into 19.6 whole square so this is equal to 19.6 square is 384 0.16 in june isn't that easy guys if you still have it out though please leave a comment below do like the channel and subscribe to our video do like the video and subscribe to our channel i'll see you in our next video until then bye guys keep learning keep flourishing"
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