Create kinetic_energy.py
diff --git a/physics/kinetic_energy.py b/physics/kinetic_energy.py
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+++ b/physics/kinetic_energy.py
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+"""
+Find the kinetic energy of an object, give its mass and velocity
+Description : In physics, the kinetic energy of an object is the energy that it
+possesses due to its motion.  It is defined as the work needed to accelerate a body of a
+given mass from rest to its stated velocity.  Having gained this energy during its
+acceleration, the body maintains this kinetic energy unless its speed changes.  The same
+amount of work is done by the body when decelerating from its current speed to a state
+of rest.  Formally, a kinetic energy is any term in a system's Lagrangian which includes
+a derivative with respect to time.
+
+In classical mechanics, the kinetic energy of a non-rotating object of mass m traveling
+at a speed v is ½mv².  In relativistic mechanics, this is a good approximation only when
+v is much less than the speed of light.  The standard unit of kinetic energy is the
+joule, while the English unit of kinetic energy is the foot-pound.
+
+Reference : https://en.m.wikipedia.org/wiki/Kinetic_energy
+"""
+
+
+def kinetic_energy(mass: float, velocity: float) -> float:
+    """
+    The kinetic energy of a non-rotating object of mass m traveling at a speed v is ½mv²
+
+    >>> kinetic_energy(10,10)
+    500.0
+    >>> kinetic_energy(0,10)
+    0.0
+    >>> kinetic_energy(10,0)
+    0.0
+    >>> kinetic_energy(20,-20)
+    4000.0
+    >>> kinetic_energy(0,0)
+    0.0
+    >>> kinetic_energy(2,2)
+    4.0
+    >>> kinetic_energy(100,100)
+    500000.0
+    """
+    if mass < 0:
+        raise ValueError("The mass of a body cannot be negative")
+    return 0.5 * mass * abs(velocity) * abs(velocity)
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod(verbose=True)

Finding the kinetic energy of an object,by taking its mass and velocity as input

### Describe your change:



* [x] Add an algorithm?
* [ ] Fix a bug or typo in an existing algorithm?
* [ ] Documentation change?

### Checklist:
* [x] I have read [CONTRIBUTING.md](https://github.com/TheAlgorithms/Python/blob/master/CONTRIBUTING.md).
* [x] This pull request is all my own work -- I have not plagiarized.
* [x] I know that pull requests will not be merged if they fail the automated tests.
* [x] This PR only changes one algorithm file.  To ease review, please open separate PRs for separate algorithms.
* [x] All new Python files are placed inside an existing directory.
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* [x] All functions have [doctests](https://docs.python.org/3/library/doctest.html) that pass the automated testing.
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* [ ] If this pull request resolves one or more open issues then the commit message contains `Fixes: #{$ISSUE_NO}`.
