The kinetic energy of a body is simply calculated using the equation

Kinetic energy Ek = ½ mv

^{2}

Where m is the mass of the mass of the object in kg

v is the velocity of the object in ms

^{-1}

As you can see the kinetic energy of the object depends on both the velocity and the mass of the object. So it is possible for an elephant with a large mass to have the same kinetic energy as a small object moving at a high velocity.

Now let us see an example where the kinetic energy of an object is calculated.

Example 1

An elephant of mass

_{3.00 x 10}

^{3}kg is moving at a velocity of 3.00 ms

^{-1}. What is the kinetic energy of the elephant?

So let us recall that the kinetic energy of the elephant is calculated using the equation

Ek = ½ mv

^{2}

Hence the kinetic energy Ek = ½ mv

^{2}

= ½(

_{3.00*}

_{10}

^{3})*(3.00)

^{2}

= 13500 J

=

_{1.35 *10}

^{4}J

Now you can be given the kinetic energy and be asked to calculate the mass or the velocity. Let us look at a second example.

Example 2

An object has a mass of 4.0 kg and a kinetic energy of 16 J. Determine the velocity of the object.

Ek = ½ mv

^{2}

16 = ½ (4.0)*v

^{2}

Making v the subject of formula

v

^{2}= (16 *2)/4.0

v = (16*2/4.0)

^{½}

v = 2.8 ms

^{-1}

Now to test your newly acquired you can do the following questions

1. Calculate the kinetic energy possessed by an aeroplane of mass

_{3.4 * 10}

^{5}kg flying at 110 ms

2. If a body has

_{3.4 x 10}

^{5}J of kinetic energy and mass

_{3.2* 10}

^{2}kg, what is its velocity?

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