Physics Basics: Motion and Quantities

Motion and Types of Motion

• Motion is a fundamental concept in physics - an object is either in rest or in motion
• An object is said to be in rest if it does not change its position with respect to its surroundings over time
• An object is said to be in motion if it changes its position with respect to its surroundings over time
• Objects can exhibit two types of motion - uniform motion and non-uniform motion

Scalar and Vector Quantities

• Physics has two types of quantities - scalar quantities and vector quantities
• Scalar quantities have magnitude (numerical value) but no direction, e.g. mass, volume, time, speed
• Vector quantities have both magnitude and direction, e.g. displacement, velocity, acceleration, force

Displacement vs Distance

• Displacement is the shortest distance between the initial and final positions of an object
• Displacement is always in a straight line, while distance is the total path length traveled
• Displacement can be equal to or less than the total distance traveled

Uniform Motion

• In uniform motion, an object travels equal distances in equal intervals of time
• The object maintains a constant speed throughout its motion
• The displacement-time graph for uniform motion is a straight line

Non-Uniform Motion

• In non-uniform motion, an object does not travel equal distances in equal time intervals

• The object's speed keeps changing during the motion

• The displacement-time graph for non-uniform motion is a curved, non-linear line### Understanding Speed and Velocity

• Speed is the rate at which distance is covered over time, while velocity is speed with a specific direction

• Speed is a scalar quantity, while velocity is a vector quantity

• Speed is measured in units like meters per second (m/s) or kilometers per hour (km/h)

• Velocity includes both speed and direction, and is measured in the same units as speed

Calculating Average Speed and Average Velocity

• Average speed = Total distance / Total time
• Average velocity = Total displacement / Total time
• For round trips, average velocity is often 0 as the initial and final positions are the same
• To calculate average speed/velocity, you need the total distance/displacement and the total time

Changing Speed vs. Changing Velocity

• Changing speed involves changing the rate at which distance is covered
• Changing velocity involves changing either the speed, the direction, or both
• Examples:
  • Increasing speed from 40 km/h to 50 km/h changes the speed but not the direction
  • Turning the steering wheel changes the direction, so it changes the velocity

Formula for Velocity

• Velocity = Displacement / Time
  • Displacement refers to the net distance covered in a specific direction
  • Time is the total elapsed time

Practice Problems

• Solving problems involving average speed, average velocity, and changes in speed/velocity

• Applying the formula v = d/t to calculate velocity given distance and time### Uniform Accelerated Motion

• Uniform accelerated motion refers to non-uniform motion where the speed is changing

• This is in contrast to uniform motion where the speed remains constant

• In uniform accelerated motion:

  • The velocity is changing
  • The acceleration is the rate of change of velocity
  • Acceleration can be positive (speeding up) or negative (slowing down)

• The three equations of motion are:

  • v = u + at
  • s = ut + 1/2 at^2
  • v^2 = u^2 + 2as

• These equations relate the initial velocity (u), final velocity (v), acceleration (a), displacement (s), and time (t)

• Using these equations, you can solve problems involving uniform accelerated motion by knowing any 3 of the 5 variables

Calculating Acceleration

• Acceleration is the rate of change of velocity
• It is calculated as: a = (v - u) / t
• Where:
  • v is the final velocity
  • u is the initial velocity
  • t is the time taken
• The unit of acceleration is m/s^2
• Positive acceleration means the object is speeding up
• Negative acceleration (deceleration or retardation) means the object is slowing down

Positive vs Negative Acceleration

• Positive acceleration means the velocity is increasing in the same direction
• Negative acceleration (deceleration) means the velocity is decreasing in the same direction
• The sign of acceleration indicates the direction, not just the speed change
• Deceleration does not necessarily mean the object is slowing down, just that the velocity is decreasing

Motion and Types of Motion

• An object is either in rest or in motion
• Rest means no change in position over time
• Motion means a change in position over time
• There are two types of motion: uniform motion and non-uniform motion

Scalar and Vector Quantities

• Scalar quantities have magnitude (numerical value) but no direction
• Examples of scalar quantities: mass, volume, time, speed
• Vector quantities have both magnitude and direction
• Examples of vector quantities: displacement, velocity, acceleration, force

Displacement vs Distance

• Displacement is the shortest distance between initial and final positions
• Displacement is always in a straight line
• Distance is the total path length traveled
• Displacement can be equal to or less than the total distance traveled

Uniform Motion

• Equal distances are traveled in equal time intervals
• Constant speed is maintained throughout the motion
• Displacement-time graph is a straight line

Non-Uniform Motion

• Unequal distances are traveled in equal time intervals
• Speed keeps changing during the motion
• Displacement-time graph is a curved, non-linear line

Understanding Speed and Velocity

• Speed is the rate at which distance is covered over time
• Velocity is speed with a specific direction
• Speed is a scalar quantity
• Velocity is a vector quantity
• Units of speed: m/s, km/h
• Units of velocity: same as speed

Calculating Average Speed and Average Velocity

• Average speed = Total distance / Total time
• Average velocity = Total displacement / Total time
• For round trips, average velocity is often 0
• Need total distance/displacement and total time to calculate average speed/velocity

Changing Speed vs. Changing Velocity

• Changing speed involves changing the rate of distance covered
• Changing velocity involves changing speed, direction, or both
• Examples: increasing speed from 40 km/h to 50 km/h, turning the steering wheel

Formula for Velocity

• Velocity = Displacement / Time
• Displacement refers to the net distance covered in a specific direction
• Time is the total elapsed time

Uniform Accelerated Motion

• Non-uniform motion where speed is changing
• Velocity is changing, acceleration is the rate of change of velocity
• Acceleration can be positive (speeding up) or negative (slowing down)
• Three equations of motion:
  • v = u + at
  • s = ut + 1/2 at^2
  • v^2 = u^2 + 2as

Calculating Acceleration

• Acceleration is the rate of change of velocity
• Calculated as: a = (v - u) / t
• Unit of acceleration: m/s^2
• Positive acceleration means speeding up, negative acceleration means slowing down