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Question
How fast should a man of 50 kg run so that his kinetic energy be 625 J?
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Solution
We have to find the speed of the running man. We have,
Mass of the man (m) = 50 kg
Kinetic energy of the man (K.E) = 325 J
So, we use the expression of kinetic energy to find the unknown quantity as,
`K.E = 1/2 mv^2`
Where,
KE - Kinetic Energy
m - Mass
v - Speed
So,
`v = sqrt((2(K.E))/((m))`
Therefore ,
`v = sqrt((2(625))/((50))` m/s
= `sqrt(25)` m/s
= 5 m/s
So , the man should be running with a speed of 5 m/s .
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