^Projectile thrown straight up

^Projectile thrown straight up

Suppose a body is projected upwards from the ground and with the velocity u. The characteristics of motion of such a body are as follows.

  1. The maximum height attained
  2. Time taken to go up (ascent) = Time taken to come down (descent)
  3. Time of flight
  4. For an object thrown straight upwards with u = 50 m/s\
  5. The speed of the body on return to the ground = speed with which it was thrown upwards
  6. When the height attained is not large, that is u is not large, the mass, the weight as well as the acceleration remain constant with time its speed, velocity, momentum, potential energy and kinetic energy change with time.
    1. Let m be the mass of the body. Then in going from the ground to the highest point, following changes take place.
    • Change in speed = u
    • Change in velocity = u
    • Change in momentum = m u

    Change in KE = Change in PE =

    1. On return to the ground the changes in these quantities are as follows:
    • Change in speed = 0
    • Change in velocity = 2 u
    • Change in momentum = 2 mu

    Change in KE = Change in PE = 0

    1. If the friction of air be taken into account, then the motion of the object thrown upwards will have the following properties:
    • Time taken to go up (ascent) < time

    taken to come down (descent)

    • The speed of the object on return to the

    ground is less than the initial speed. Same is true for velocity (magnitude), momentum (magnitude) and KE.

    • Maxi height attained is less than .
    • A part of the KE is used up in overcoming

    the friction.


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