Question

a moving body of 30 kg has 60 joule of kinetic energy calculate the speed
please explain fast very urgent.​

Answer 1

Given :-

Mass of the body (m) = 30kg

Kinetic energy = 60J

To Find :-

Speed (v)

Solution :-

We know :-

Kinetic energy = ½ mv²

➟ 60 = ½ × 30 × v²

➟ 60 = 15 × v²

➟ v² = ⁶⁰⁄₁₅

➟ v² = 4

➟ v = √4

➟ v = 2

Speed of the body is 2 m/s.

Answer 2

Solution:

Kinetic energy of a moving body = 60J

Mass of a moving body = 30kg

Speed of a moving body = ??

$\tt{E_K= \frac{1}{2}mv^2}$

$\tt \therefore{v =\sqrt{ \frac{2E_K}{m} }}$

$\rm\implies{v = \sqrt{ \frac{2(60)}{30} } }$

$\rm\implies{v = \sqrt{ \cancel\frac{120}{30} } }$

$\rm\implies{v = \sqrt{4} }$

$\rm\implies{v = 2}$

Hence, the speed of a moving body is 2m/s.

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Additional Information:

Kinetic energy depends on the following factors:

• Mass of the body: Kinetic energy of a body is directly proportional to its mass. This means heavier the body, more is its kinetic energy.

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• Speed of the body: Kinetic energy of a body is directly proportional to the square of its speed. This means a fast moving body will have more kinetic energy than a body of same mass having slower speed. That is why an accident of a fast moving car is more fatal.

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Hence, if we consider a body of mass m moving with speed v, then kinetic energy possessed by it is given by:

$\bf{E_K= \frac{1}{2}mv^2}$

According to this relation, if mass of the body is doubled, its kinetic energy will be also doubled. However, if speed of the body is doubled, its energy will increase four times.

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