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JEE Main 202131 AugustMorning Shift
Exam
JEE Main
Year
2021
Date
31 August
Shift
Morning Shift
Subject
Physics
Chapter
Work, Power and Energy

JEE Main 2021 · 31 August · Morning Shift · Physics · Work, Power and Energy

A block moving horizontally on a smooth surface with a speed of 40...

A block moving horizontally on a smooth surface with a speed of 40ms−140{ms}^{- 1} splits into two equal parts. If one of the parts moves at 60ms−160{ms}^{- 1} in the same direction, then the fractional change in the kinetic energy will be x:4x: 4 where x=x = ________.A block moving horizontally on a smooth surface with a speed of 40 ms ^ - 1 splits into two equal parts. If one of the

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Step-by-step solution

A block moving horizontally on a smooth surface with a speed of 40 ms ^ - 1 splits into two equal parts. If one of the2m×40=60×m+mv2m \times 40 = 60 \times m + mv
V=20m/sV = 20m / s
Now \DeltaKE=KEf−KEi=12m×(20)2+12m×(60)2−122m×(40)2\DeltaKE = K{E}_{f} - K{E}_{i} = \dfrac{1}{2}m \times ( 20{)}^{2} + \dfrac{1}{2}m \times ( 60{)}^{2} - \dfrac{1}{2}2m \times ( 40{)}^{2}
\DeltaKE=12m(800)⇒KEi=122m×(40)2=12m×3200\DeltaKE = \dfrac{1}{2}m ( 800 ) ⇒ K{E}_{i} = \dfrac{1}{2}2m \times ( 40{)}^{2} = \dfrac{1}{2}m \times 3200
Fractional change =\DeltaKEKEi=14= \dfrac{\DeltaKE}{K{E}_{i}} = \dfrac{1}{4}

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