Question

mass of 10 kg is dropped from 50 cm find its velocity and kinetic energy

Answer 1

Given:-  m = 10kg

h = 50cm = 50x10-2m

P.E. = mgh = 10x10x50 x10-2 (Take g = 10 m/s2)= 50J

When it is dropped from the height initial velocity u = 0 m/s

according to equation

v2-u2=2gh

v2-0=2x10x50x10-2



K.E. = ½ mv2 = ½ x 10x10 = 50J

when mass will hit the ground it will have same kinetic energy as that was potential energy before dropping. This is also in agreement with law of conservation of energy which states that energy transforms form one form to another.

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OR
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mass=m=10 kg

g=10m/s

h=50cm=0.5m

P.E=mgh

      =10*10*0.5

      =50J

to find velocity

2gh=vf2-vi2

as body is falling its vi is zero

2*10*0.5=(v)2-(0)2

10=v2

taking square root

3.2m/s=v

K.E=1/2mv2

      =1/2*10*10

      =50J

 we also know that  

P.E at top=K.E at bottom 

so as P.E is 50 J K.E will also be 50J

=10*10*0.5

=50J