ADVANCED PHYSICS

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A force is a push, pull or twist that can be exerted on a body or object. A force is a vector quantity, requiring magnitude, direction and a point of application for its description.

 Consider Newton's First law of motion, which states:

 An object will remain at rest or continue with uniform motion in a straight line unless acted upon by some external force.

 Therefore in order to change the motion of a body a force must be applied. For example, a spacecraft in space will travel with a constant speed and in a straight line, unless it experiences a force from the gravitational field of a planet attracting it, or its engines creating thrust. To change the motion or velocity of a body, that is, to accelerate it, it requires a force. According to Newton's 2nd law:

 The acceleration of a body is proportional to the applied force, and inversely proportional to the mass of the body or

F = m a

Where F is the force in N, m is the mass of the body in Kg, and a is the acceleration in m/s

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