**Linear Motion**is the motion of an object in a straight line

**.**

**Kinematics**is the study of the of motion objects without considering the forces that cause the motion of the object

**.**

**Distance**is the total length of the path covered by a moving object.

**Displacement**is distance from one point to another in a particular direction.

**Speed**is rate of change of distance. Unit

*m s*

^{-1}^{}

**Velocity**is the rate of change of displacement.

**Average speed**is total distance moved divided by total time taken.

**Average velocity**is total displacement divided by total time taken.

**Acceleration**is rate of change of velocity. Unit

*m s*

^{-2}

*a =*

__v - u__*t*

Equations of linear motion with uniform acceleration are as follows :

v = u + at

s = ut + ½ at

^{2}
v

^{2}= u^{2}+ 2 as**Dynamics**is the study of the motion and of the forces that cause the motion of that body.

**Inertia**is the resistance of an object to change of its motion. Inertia is non-physical quantity.

**Mass**of an object

**is the quantity of matter in that object.**

**Newton’s First Law of motion**states

**,**if no external force is acting on an object, it will, if stationary remain stationary, if moving keep moving at a steady speed in a straight line.

**Momentum**of an object is defined as a product of mass and its velocity. Unit

*kg*

*m s*

^{-1}

*p = mv*

**Principle of conservation of momentum**states that when two or more objects act on each other, their total momentum remains constant, provided there are no external forces acting on the system.

*(m*

_{1}u_{1}+ m_{2}u_{2}= m_{1}v_{1}+ m_{2}v_{2})
Force
acting on an object can cause changes to its size, shape, and state of rest,
velocity, and direction of motion of the object.

**Newton**

**’s second law of motion**states that force acting on an object is directly proportional to the rate of change momentum of the object in the same direction.

*F = ma***Impulse**is the product of force and time for which the force acts during collision

**Impulsive force**is the force that acts on an object within a very short time such as during a collision.

F
= mv – mu t |

**Gravitational attractive force**is the pull (force) of the earth on objects and it acts towards the centre of the earth

An
object is in

**free fall**when it falls under the influence of gravitational attractive force**without the influence of other forces. (A****free fall**is situation whereby an object falls under the influence of gravitational attractive force**only).****Gravitational acceleration**is the acceleration of an object which falls freely.

**Weight**of an object is the gravitational force acting on it. Or

*W = mg*(

*m*= mass,

*g*= gravitational acceleration)

An object is in

**equilibrium**if the resultant of forces acting on it is**zero**.**Newton’s Third Law of Motion**states that for every force there is an opposite an equivalent force against it.

**A resultant force**is a single force that represents in magnitude and direction two or more forces acting on an object.

**Resolving a force**is replacing a single force by a pair of perpendicular forces provided that the resultant of the two forces is equivalent to the single force.

**Work done**by constant force to move an object is equivalent to the product of the magnitude of its displacement and the components of the force, which is in the direction of the displacement.

W = F x
s

**Energy**is defined as the capacity of a system to do work.

**Gravitational Potential Energy**is defined as energy obtained by an object due to its position.

**E**

_{p}= W = Fs**= mg x h**

**= mgh**

**Elastic Potential Energy**is defined as energy obtained by object due to its state (extension or compression)

**E**

_{p}= ½ F x**Kinetic Energy**is defined as energy attained by an object due to its motion.

**W = E**

_{k}= ½ m v^{2}**Conservation of Energy**states that energy cannot be created nor destroyed but changes from one form to another.

**Elasticity**of a material is its ability to return to its original form and size when the force acting on it is removed.

**Hooke’s law**states that the extension of an elastic spring is directly proportional to the force acting on it provided that the limit of elasticity is not exceeded.

**Spring constant**is defined as force per unit extension of a spring.

A
soft spring has a smaller

*k*value whereas a stiff spring has a larger*k*value.
The

**work done**when extending or compressing an elastic material is given by
The s

**trength**of a material is the ability of the material to withstand external forces before it breaks or snaps. Rattan is a strong but not rigid material. Concrete is both strong and rigid.**Rigidity**is the ability of a material to withstand external forces acting on it without changing its size or shape. Glass is a rigid but not a strong material.

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