Resisted motion help (1 Viewer)

[girrawhat]

Hey guys. I have my trial very soon and i can't get my head around resisted projectile motion. Any tips or handy hints that will make life easier?

 

[SpiralFlex]

Perhaps posting some questions you don't understand.

 

[girrawhat]

Here is an example

A ball is thrown at an angle alpha to the horizontal from the top of a very high building. Its initial velocity is u. It experiences air resistance of mkv directed against each of the x and y components of its motion. Its vertical component also experiences effect of gravity.

a) Given that force in horizontal direction is mkv against motion, state acceleration (x double dot), and show that
velocity (x dot) = Ucosalphae^-kt
x= (ucosalpha/k)[1-e^ikt]

State the distance which x can never exceed if u=40m/s, k=0 and alpha=45 degrees.

b) Given that air resistance vertically against ball is mkv and gravity is affecting ball, state (y double dot) and show that
t= (-1/k) ln[ (kv+g)/(kusinalpha + g)]

Find the maximum height of the ball

 

[Carrotsticks]

It's the EXACT same thing as normal Resisted Motion, except your initial conditions are the same as the ones for projectile motion with the whole Vcosx and Vsinx deal.