Motion in One Dimension

Motion in One Dimension

1. Physical Quantities: Quantities that can be measured are known as Physical Quantities.

   • Scalars - Physical quantities which are expressed only by their magnitude.
     • Parameters to express it completely: [a] Unit (If the scalar is a pure number like π it will have no unit) [b] Numerical value
       • EXAMPLES: Mass, length, distance, density, volume, speed, temperature, power, pressure, charge, frequency, etcetera
   • Vectors - These physical quantities require magnitude as well as the direction to express them. It's only then their meaning is complete
     • Parameters to express it completely: [a] Unit [b] Direction [c] Numerical Value
       • EXAMPLES: displacement, velocity, accelaration, mementum, force, torque, impulse, weight, etcetera.

2. REST AND MOTION: The body is tend to be in rest or motion if it does not change its position with respect to its immediate surroundings.

   • ONE DIMENSIONAL MOTION / RECTILINEAR MOTION: When a body moves along a straight line path
   • TWO DIMENSIONAL MOTION: When a body moves along a curved line path
   • THREE DIMENSIONAL MOTION: When a body moves in space

3. DISTANCE AND DISPLACEMENT

   • DISTANCE: The total length of the path along which a body moves, is called the distance travlled by it.
     • It is a scaler quantity
     • SI UNIT - Metre (m) CGS UNIT - centimeter (cm)
   • DISPLACEMENT: The shortest distance from the initial to the final position of the body, is the magnitude of displcament and its direction is from the inital position to the final position
     • It is a vector quantity
     • SI UNIT - Metre (m) CGS UNIT - centimeter (cm)
     • DISTINCTION
       • The magnitude of the displacement will always be either equal to or less than distance
       • Distance is always positive but displacement can be either positive or negative
       • The displacement can be zero even if distance is not

4. SPEED AND VELOCITY

   • SPEED: The speed of a body is the rate of change of distance with time.
     • It is a scaler quantity. SI UNIT: m/s CGS UNIT: cm/s
       • UNIFORM SPEED: A body is said to be moving with uniform speed if it covers equal distances in equal intervals of time throughout its motion.
       • NO UNIFORM/ VARIABLE SPEED: A body is said to be moving with non-uniform (or variable) speed if it covers unequal distances in equal intervals of time.
       • INSTANTANEOUS SPEED: When the speed of a body keeps on changing, its speed at any instant is measured by finding the ratio of the distance travelled in a very short time interval to the time interval.
       • AVERAGE SPEED: The ratio of the total distance travelled by the body to the total time of journey is called its average speed.
   • VELOCITY: The velocity of a body is the distance travelled per second by the body in a specified direction
     • It is a vector quantity. SI UNIT: m/s CGS UNIT: cm/s
       • UNIFORM VELOCITY: If a body travels equal the average veloc distances in a particular direction, in equal intervals of time, the body is said to be moving with variable velc with a uniform velocity.
       • NO UNIFORM/ VARIABLE VELOCITY: The velocity of a body can be variable either due to change in its magnitude or in its direction or in both magnitude and direction.
       • INSTANTANEOUS VELOCITY: For a body moving with variable velocity, the velocity of the body at any instant is called its instantaneous velocity.
       • AVERAGE VELOCITY: If the velocity of a body moving in a particular direction changes with time, the ratio of displacement to the time taken in the entire journey is called its average velocity.
     • DISTINCTION
       • Speed is a scalar quantity, while velocity is a vector quantity.
       • For the motion in a straight line, the magnitude of velocity is its speed. The speed is always positive, but velocity is given a positive or negative sign depending upon its direction of motion.
       • The average velocity of a body can be zero, even if its average speed is not zero.