Describing Motion Around Us and Kinetics

Introduction to Motion and Kinetics

  • Date: 6/7/26

  • Kinetics: The branch of science that studies the motion of object is called kinetics.

  • Definition of Motion: It is the change in the position of an object with time, with respect to a reference point.

  • Condition for Motion: An object is said to be in motion only when its position changes continuously with time.

  • Example of Motion: A train passes a railway station.

    • Reference Point: The railway station.

    • Explanation: The train changes its position with respect to the railway station, so it is called motion.

Distance

  • Definition: Distance is a total length of the actual path travelled by an object, respect of its welled by an object, direction.

  • Purpose: It tells us how much ground an object has covered.

  • Physical Quantity Type: Distance is a scalar quantity, which means it has only magnitude.

  • Characteristics:

    • It is always positive.

    • It can never be negative.

  • Unit: The standard measurement for distance is meter (m\text{m}).

  • Example Scenario: A walk involving two legs: 10 m10\,\text{m} East followed by 5 m5\,\text{m} South.

    • Total Distance Calculation: 10+5=15 m10 + 5 = 15\,\text{m}.

Displacement

  • Definition: Displacement is the shortest straight line distance between the initial position and final position of an object, along with the direction.

  • Purpose: It tells us how far and in which direction an object has moved.

  • SI Unit: The unit of displacement is also the meter (m\text{m}).

  • Reference Timeline/Values:

    • t=0 st = 0\,\text{s} at 0 m0\,\text{m}.

    • t=4 st = 4\,\text{s}.

    • t=10 st = 10\,\text{s} at 100 m100\,\text{m}.

    • Linear markers provided: 0 m0\,\text{m}, 20 m20\,\text{m}, 40 m40\,\text{m}, 60 m60\,\text{m}, 80 m80\,\text{m}, 100 m100\,\text{m}.

Speed and Uniform Motion

  • Average Speed: The average speed of a body is the total distance travelled divided by the total time taken to cover this distance.

  • Formula for Average Speed: Average speed=Total distance travelledTotal time taken\text{Average speed} = \frac{\text{Total distance travelled}}{\text{Total time taken}}

  • Uniform Speed: A body has a uniform speed if it travels equal intervals of time (equal distance), no matter how small time interval may be.

Exercise and Unit Conversions

  • Exercise 1: A person covers the distance of 3 km3\,\text{km} in 5 min5\,\text{min}. Calculate his speed in:

    • cm/s\text{cm/s}

    • m/s\text{m/s}

    • km/h\text{km/h}

  • Standard Unit Conversion Library:

    • 1 km=1000 m1\,\text{km} = 1000\,\text{m}

    • 1 m=100 cm1\,\text{m} = 100\,\text{cm}

    • 1 cm=10 mm1\,\text{cm} = 10\,\text{mm}

    • 1 hr=60 min1\,\text{hr} = 60\,\text{min}

    • 1 min=60 sec1\,\text{min} = 60\,\text{sec}