A body of mass 5 kg is thrown verticallywith a kinetic energy of 490 J

1.	A body of mass 5 kg is thrown verticallywith a kinetic energy of 490 J. The heightwhich the kinetic energy of the body beconhalf of the original value is(1) 12.5 m (2) 10 m (3) 2.5 m (4) 5 n
Answer» Let u be the velocity with which it was projectedK = 0.5mu²490 J = 0.5 × 5 kg × u²u² = 196 J/kg Let v be the velocity at the point where it’s kinetic energy becomes half is490/2 = 0.5 mv²490 Joule = 5 kg × v²v² = 98 Joule/kg Now, use equation of motion v² - u² = 2aSh = [(98 - 196) J/kg] / (2 × -9.8 m/s²) = 5 m K.E will become half at height of 5 m

A body of mass 5 kg is thrown verticallywith a kinetic energy of 490 J. The heightwhich the kinetic energy of the body beconhalf of the original value is(1) 12.5 m (2) 10 m (3) 2.5 m (4) 5 n

Answer»

Let u be the velocity with which it was projectedK = 0.5mu²490 J = 0.5 × 5 kg × u²u² = 196 J/kg

Let v be the velocity at the point where it’s kinetic energy becomes half is490/2 = 0.5 mv²490 Joule = 5 kg × v²v² = 98 Joule/kg

Now, use equation of motion v² - u² = 2aSh = [(98 - 196) J/kg] / (2 × -9.8 m/s²) = 5 m

K.E will become half at height of 5 m

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A body of mass 5 kg is thrown verticallywith a kinetic energy of 490 J. The heightwhich the kinetic energy of the body beconhalf of the original value is(1) 12.5 m (2) 10 m (3) 2.5 m (4) 5 n

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