Motion and Time
Motion
➥ Motion: An object is said to be in motion if it changes its position with respect to time.
Example: A car moving on a road.
➥ Rest: An object is at rest if it does not change its position with time.
Example: A person standing on the ground.
Distance and Displacement
- Distance: The total path covered by an object in a given time.
Formula:Distance = Speed × Time
➯ Unit: Meters (m) or Kilometers (km). - Displacement: The shortest path covered by the moving object in the given interval of time.
Basics of Standard Units
- Distance: Standard unit is meters (m).
- Time: Standard unit is seconds (s).
- Speed: Standard unit is meters per second (m/s).
Types of Motion
- Rectilinear/Translatory Motion: Motion in a straight line without changing direction.
Example: A car moving on a straight road. - Circular Motion: Motion in the shape of a circle about a fixed point and radius.
Example: Planets revolving around the Sun. - Rotational motion: The motion possessed by a body when it spins about a fixed axis, is called rotational motion.
e.g. the motion of the earth about its axis, spinning top, the motion of blades of a fan. - Periodic/Oscillatory Motion: Motion that repeats after fixed intervals of time.
Examples: To-and-fro motion of a simple pendulum, Earth's rotation.
Oscillations of a Simple Pendulum
Oscillation: When the bob of a pendulum moves from one extreme position, passes the mean position, and returns to the same extreme position, it completes 1 oscillation.
Simple Pendulum:
➥ A pendulum is a weight suspended from a fixed point that swings back and forth under the influence of gravity.
Applications:Used in clocks and scientific experiments.
Fast and Slow Motion
Fast Motion➥ Fast motion occurs when an object moves over a large distance in a small amount of time. For example:
eg:-
A car moving on a highway.
A rocket launching into space.
➯ In fast motion, the speed of the object is high, meaning the object covers a lot of distance in a short period of time.
Slow Motion➥ Slow motion happens when an object moves over a small distance in a long period of time. Examples include:
eg:-
A tortoise walking slowly.
A snail moving at a very slow pace.
➯ In slow motion, the speed is low, meaning the object covers less distance in the same amount of time.
Speed (Average Speed)
➥ Speed is the total distance traveled by an object in a given interval of time.
Speed = Distance traveled / Time taken
➯ The unit of speed is generally measured in metres per second(m/s), kilometres per hour(km/h).
Uniform and Non-Uniform Motion
Uniform Motion: An object moving in a straight line at a constant speed.
Example: A car traveling in a straight line at a constant speed.
Non-Uniform Motion: An object moving in a straight line with a varying speed over time.
Example: The motion of a train.
Measurement of Time
➯Ancient Methods of Measuring Time:
Sundial: Used shadows cast by the sun to measure time.
Water Clocks: Measured time based on the flow of water.
Sand Clocks (Hourglasses): Measured time using the flow of sand.
Mechanical Clocks: Introduced gears for more accurate measurement.
➯ Modern Methods:
Quartz Clocks: Use vibrations of quartz crystals.
Atomic Clocks: Measure time based on vibrations of atoms (most accurate).
Units of Time
Second is the basic unit (or standard unit) of measuring time and it is represented by symbol s.
The larger units of time are minute and hour.
i.e. 1 h = 60 min and 1 min = 60 s
Different units of time are used depending on the need, e.g. in order to express the longer time interval, the bigger units of time are used, i.e. day, month and year.
i.e. 1 day = 24 h, 1 month = 30 days and 1 year = 12 months
Modern Clocks:
Quartz Clocks: Modern clocks use electric circuits and quartz crystals to measure time. They provide highly accurate time measurements compared to traditional clocks.
Speedometer and Odometer
Speedometer: Measures the speed of a vehicle directly in km/h.
Odometer: Measures the total distance traveled by a vehicle in km.
Visualizing Motion
Distance-Time Graph: A distance-time graph is a graph plotted between the distance (in the y-axis) and time (in the x-axis).
Interpretation:
Slope: Indicates the speed of an object.
Steeper slope = Higher speed
Flat line = Object at rest
Graph Types:
- Straight Line:➝ Uniform motion
- Curved Line:➝ Non-uniform motion
- Horizontal Line:➝ Object is stationary
0 Comments