Geometrical Optics
ALLIANZE UNIVERSITY COLLEGE OF MEDICAL SCIENCES
Physics Lab Experiment
Geometrical Optics
Name :
INTRODUCTION
Friction is a force (measured in Newtons) acting along the surfaces of two objects in physical contact that impedes the relative motion of these objects (the motion of one with respect to the other). As such, it can be said that friction always acts opposite the motion of the object or the force applied.
There are two main types of friction:
Static friction: the frictional force that opposes any attempt to move a stationary object along a surface.
Kinetic friction: this frictional force opposes the sliding motion of two surfaces rubbing together.
Physically, friction arises from surface roughness and attractive forces between the surfaces of two objects in contact.
The frictional force depends on how hard the surfaces are pushed together: usually that quantity is calculated by determining the surface ‘normal’ force (Fn).
The harder the surfaces are pushed together, the more surface contacts are made, increasing friction. Interestingly, friction does not depend on the surface area of the objects in contact. This is because as the area gets larger, the force per unit area gets smaller, decreasing the number of points in physical contact. Some of the characteristics of static and kinetic friction are:
Static friction:
Kinetic friction:
Designated as fs
Proportional to Fn(surface normal force)
Independent of area
Variable to a maximum value (which depends on the surfaces)
Designated as fk
Proportional to Fn
Independent of area
Independent of speed
Always less than static friction
Let’s examine the relationship between these two forces and the applied force that creates them (they can be thought of as "reaction" forces). If you observe the graph below, it shows the static frictional force increasing to a maximum with the application of a force ("applied force") then
Physics Lab Experiment
Geometrical Optics
Name :
INTRODUCTION
Friction is a force (measured in Newtons) acting along the surfaces of two objects in physical contact that impedes the relative motion of these objects (the motion of one with respect to the other). As such, it can be said that friction always acts opposite the motion of the object or the force applied.
There are two main types of friction:
Static friction: the frictional force that opposes any attempt to move a stationary object along a surface.
Kinetic friction: this frictional force opposes the sliding motion of two surfaces rubbing together.
Physically, friction arises from surface roughness and attractive forces between the surfaces of two objects in contact.
The frictional force depends on how hard the surfaces are pushed together: usually that quantity is calculated by determining the surface ‘normal’ force (Fn).
The harder the surfaces are pushed together, the more surface contacts are made, increasing friction. Interestingly, friction does not depend on the surface area of the objects in contact. This is because as the area gets larger, the force per unit area gets smaller, decreasing the number of points in physical contact. Some of the characteristics of static and kinetic friction are:
Static friction:
Kinetic friction:
Designated as fs
Proportional to Fn(surface normal force)
Independent of area
Variable to a maximum value (which depends on the surfaces)
Designated as fk
Proportional to Fn
Independent of area
Independent of speed
Always less than static friction
Let’s examine the relationship between these two forces and the applied force that creates them (they can be thought of as "reaction" forces). If you observe the graph below, it shows the static frictional force increasing to a maximum with the application of a force ("applied force") then
References: 1. (Newton’s Mechanics) http://library.thinkquest.org/C0125108/eng/nor/page4-1.htm 2. (Friction) http://www2.ignatius.edu/faculty/decarlo/friction3.htm 3. College Physics Giambattista Richardson Book