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Give any two salient features of static Friction and Kinetic Friction. |
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Answer» Solution :Static friction: Static friction is the force which opposes the initiation of motion of an object on the surface. The MAGNITUDE of static force `f_(s)` lies between. `=lef_(s)lemu_(s)N_(s)` `mu_(s)`- coefficient of static friction N- Noemal force Kinetic frition : The frictionl force excerted bysurface when an object slides is called as kinectic friction . Also called as sliding friction or dynamic friction, (ii) To move an object-pushior pull? Which is easier? Explain When a body is pushed at an ARBITRARY angle `theta (0 "to"(pi)/(2))`,the applied force F can be resolved into two componentes as F `sin theta` parallel to the surface and F `cos theta ` perpendiculerto the surface as shown in figure. The total downward force acting on the body is mg+F `cos theta` . It implies that the normal force acting on the body increas. Since there is no acceleration alon the vertical direction the normal force N is equal to. `N_(PUSH)=mg+F costheta` As a result the maximal static friction also increasesand is equal to `f_(x)^(MAX)=mu_(r)N_(PUSH)=mu_(5)(mg+fcostheta)` Equation (2) SHOWS that a GREATER n force needs to be applied to push the object into motion .  When an object is pulled at an angle `theta`, the applied force is resolved into two components as shown in figure. the total downward force acting on the object is `N_(pull)=mg-Fcostheta`  Equation (3) shows that the normal force is less than `N_(push)`. from equations (1) and (3), it is easier to pull an object than to push to MAKE it move. |
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