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    Chapter 2

    Uploaded by

    Muhammad Saqib Baig

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    © All Rights Reserved
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    Chapter 2

    Uploaded by

    Muhammad Saqib Baig
    2 views16 pages

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    2 views16 pages

    Chapter 2

    Uploaded by

    Muhammad Saqib Baig

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 16

    Applied Physics

    Chapter 2
    Motion along straight line
    BSEE-19
    Aircraft
    Speed of aircraft at take-off
    should be 250–300 km/h

    The jet engines quickly


    accelerates the aircraft from zero
    to take-off speed in matter of few
    seconds

    Magnitude of acceleration during


    launch?
    Distance travelled by aircraft ?
    Mechanics
    The branch of physics that deals with motion of bodies is called
    mechanics

    Mechanics is divided into


    • Kinematics (motion of objects without reference to the forces which cause
    the motion, e.g. position, velocity, and acceleration)
    • Dynamics (deals with force as the cause of changes in motion, e,g, lift, thrust,
    weight, etc)
    Average Speed
    The average speed of the particle is defined as the ratio of this
    distance and the time taken.

    The SI unit of speed is the meter per second (m/s).


    Average Speed
    In general everyday objects
    speed is often measured in
    kilometers per hour (km/h):

    1000 𝑚
    1 km/h = = 0.278 m/s
    3600 𝑠
    Mountain Height
    Nangaparbat at 8,125 meters is
    growing at 7 mm/year in height,
    which is the fastest of any major
    mountain and almost twice that of
    Mt. Everest at 8,848 meters.

    Everest’s growth is 4 mm/year.

    Hence, Nangaparbat is estimated


    to overtake Mt. Everest in
    approximately 241,000 years and
    become the highest mountain on Mount Nangaparbat, Pakistan as seen from Sheosar Lake 60 km away
    planet Earth.
    https://www.guinnessworldrecords.com/world-records/fastest-
    rising-mountain/
    Example
    The world record set by Usain Bolt in 2009 for the
    100-m run was 9.58 s. What average speed did he
    attain while setting this record?

    Average speed = total distance travelled = 100 m = 10.4 m/s


    time taken 9.58 s
    Relative Motion

    Motion and speed are relative


    Questions
    QUESTION 1: A man takes 100 s to walk 50 m along a straight
    road.What is his average speed? A woman jogs the same distance in
    50 s, and then stands at the endpoint for 50 s.What is her average
    speed over the 100-s interval?

    QUESTION 2: Consider a runner running at 10 m/s relative to the


    surface of the Earth and consider a spectator standing at rest on the
    surface of the Earth. A bicyclist is riding in the same direction as the
    runner, but at a different speed. Is it possible that in the reference
    frame of the bicyclist the spectator has a larger speed than the
    runner? That the spectator and the runner have equal speeds?
    Average Velocity
    The average velocity is defined as the ratio of this change of position
    and the time interval:

    Velocity is a vector quantity while speed is a scalar quantity.


    Speed is always positive, whereas velocity is positive or negative
    depending on the direction of motion.
    Average Velocity
    Average Velocity
    Average velocity is the
    ratio of the vertical
    separation between the
    points P1 and P2 and the
    horizontal separation.
    Velocity signs
    Sign of velocity depends on the direction of motion

    Positive x-direction  velocity is positive


    Negative x-direction  velocity is negative
    Example
    Instantaneous Velocity
    Instantaneous Velocity is the velocity at one
    instant of time.

    Example: Speedometer of your car or bike


    displays the magnitude of instantaneous
    velocity!

    A moving automobile or a moving particle


    does not cover any distance in one instant so
    how to define instantaneous velocity?

    Particle moving with constant velocity has


    instantaneous velocity coinciding with
    average velocity

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