Phy Chapter 6 Introduction To Forces Ok Caltec S.2

CHAPTER SIX INTRODUCTION TO FORCE 5.1 Force Force is either a push or pulls that acts on an object. Or Force is that which changes a body’s state of rest or uniform motion in a straight line. A force cannot be seen and described like an object, but the effects of force on an object can be seen. Just like we can not see wind but we can feel and see the effects in a flying flag or kite or in a tree bending. (a) SI Unit of force The SI unit of force is called Newton (N) and is defined as follows: A Newton is the force required to give a mass of one kilogram an acceleration of one metre per Second Squared. Representation of force Force is a vector quantity i.e. it has both magnitude and direction. It is represented by a straight line with an arrow at the tip showing the direction in which it acts. (c) Effects produced by a Force A force acts in a particular direction and may have any of the following effects on an object. It can: (i) Make a stationary object to move. (ii) Increase the speed of a moving object. (iii) Decrease or slow down the speed of a moving object or bring a moving object to a rest. (iv) Change the direction of a moving object. (v) Deform (change the shape of) an object. (d) Types of Forces There are various types of forces; some of the common ones include the following: (i) Gravitational force - is the force which pulls a body towards the centre of the earth. (ii) Frictional force - is the force which opposes relative motion between two surfacesin contact. (iii) Centripetal force - is a force which constrains a body to move in a …