This document discusses rectilinear acceleration and defines key concepts related to forces and friction. It defines acceleration, uniform and non-uniform acceleration, and deceleration. It describes two types of forces - contact forces and non-contact forces. It further discusses friction, the different types of friction, and factors that affect friction. Finally, it outlines the laws of solid friction and provides examples of dimensional analysis.
3. DEFINITION OF FORCE
SS1PHYS
A push or pull on the body is a force that
caused the motion.
Force can be defined as that which alters the
state of rest or motion of a body in a straight
line. This is what actually causes a motion of a
body. It moves a body, change its direction ,
slow its motion or stop its motion
TYPES OF FORCES
There two types of forces namely:
(1) Contact forces
(2) Non- Contact Forces (Field forces )
4. SS1PHYS
CONTACT FORCES : These are
forces which are in contact or in touch with
the body to which are supplied. E.g. A pull,
a push, tension, reaction, frictional force
NON-CONTACT FORCES: These are
forces whose do not require contact with
the body to which they are applied. E.g.
gravitational force, electric force, magnetic
force.
TYPES OF FORCE
5. SS1PHYS
FRICTION: Friction is the force which acts at
the surface of separation b/w two bodies in
contact & tends to oppose the motion of one over the
other.. It acted tangential to the surface of separation.
In as much as one body move over another, frictional
force continue to act.
TYPES OF FRICTION
Static Friction: Static or limiting friction is the
maximum force that must be overcome before a body
can just begin to move over another.
Kinetic Friction: Kinetic or dynamic friction is te
force that must be overcome so that a body can move
with uniform speed over another body. E.g. sliding &
rolling frictions.
6. FACTORS AFFECTING FRICTION
(1) Nature of surface : If there is
more roughness on the object surface,
more friction & less roughness brings
less friction
(2) Weight(normal force): The more the
weight of a body, the more the frictional
force.
(3) The surface in contact: The larger the
surface area the larger the frictional force
SS1PHYS
7. LAWS OF SOLID FRICTION
SS1PHYS
Experimental results lead to the following
laws of solid friction;
o Friction opposes relative motion b/w two
surfaces in contact
o Frictional force increases to the same extent as
the force which tends to start the motion.
o Frictional force depends on the nature of the
two surfaces in contact.
o It is independent of the area of the surfaces in
contact
o It is directly, proportional to the normal
reaction R
8. (1) It enable us to walk.
(2) It enable vehicle tyre to make a firm grip
with the road.
(3) It is used in belt drive, transmitting
motion from one pulley to another without
slipping.
(4) It enables screw and nails to remain in
place after being fastened.
(5) It enables brakes of vehicle to hold.
(6) It is used in grinding stones to sharpen
objects bcos of their abrasive (rough) surface.
ADVANTAGES OF FRICTION
9. (1) Prefixes are used for magnitude of
physical quantities vary over a wide range. The
international standard prefixes for certain powers of 10
are;
DISADVANTAGES OF FRICTION
10. Dimensions are the powers to which the
fundamental units of Mass, Length & Time must be
raised to represent the physical quantity.
E,g, Force = mass x acceleration
Unit = (M x L/T10-2)
Hence, force dimension are M=1. L=1 & T= -2
Dimensional formula
Dimensional formula is the expression of unit of a
physical quantity in terms of M, L & T. It actually
shows how & which of the fundamental quantities
represent the dimension. The dimensional equation of
a physical quantity Y is given by
Y = [MaLbTc}
DIMENSION
11. Ex1. Dimensions are the powers to which the
fundamental units of Mass, Length & Time must be
raised to represent the physical quantity.
E,g, Force = mass x acceleration
Unit = (M x L/T10-2)
Hence, force dimension are M=1. L=1 & T= -2
Dimensional formula
Dimensional formula is the expression of unit of a
physical quantity in terms of M, L & T. It actually
shows how & which of the fundamental quantities
represent the dimension. The dimensional equation of
a physical quantity Y is given by
Y = [MaLbTc}
EXAMPLES & CLASSWORK
