Gramin ACS College Vasantnagar, Kotgyal � MATHEMATIS

B.Sc. Final Year Paper-14^th (Mechanics)

Sem-V

PPT Presented by.....

Prof. Dr. P. R. Shinde

Department of Mathematics

Gramin ACS college Vasantnagar, kotgyal

Tq: Mukhed Dist: Nanded ( M.S) INDIA

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Force acting on a rigid body

• Introduction: In this chapter we shall discuss about the forces acting on a rigid body , which is defined as system of particle , the distance between which remain invariable. If a force acts on a particle, it causes the motion of translation in it in the direction of the force.

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• When a system of forces acts on a rigid body, then its displacement is a characterized by the following two kinds of motion:

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• i) Motion of translation : which has the same magnitude and direction for each particle of the rigid body, and
• ii) Motion of rotation about some fixed point in the rigid body and which has different magnitude and direction for each particle depending on its position relative to the fixed point.

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• Moment of a force :

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• Suppose a force F acts at a point P of rigid body and O is some fixed point in its plane. Let p be the length of the perpendicular from O to the line of action of the force F . Then the product F•p is known as the moment of the force F about O.

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• i.e. Moment of the force F about O= F•p = |F|•p

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• If we consider more than one force acting on a body , there are two types of rotation that occurs in anti clockwise and clockwise

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• Direction respectively, the moment of the force F shout O is +ve or -ve according as the rotation is in anti clockwise or clock wise direction. Thus, we find the vector moment which is represented by magnitude and direction as well.

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Where e is the unit vector perpendicular to be the plane containing r and F and in the direction of the vector

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F