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knightryder
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Homework Statement
Hello everyone - here's my question: I am doing an assignment on projectile motion and I will be launching some balls from a compressor (that I have not seen yet!). I know how to calculate how much work will be done by the air expanding (will obv. depend on how much pressure is in the compressor); but i do not know how to go from there:
do i say that the work done will equal the kinetic energy of the ball and just use the simple projectile motion formulae? If i do, isn't that neglectling the time taken for the ball to accelerate?
If I take acceleration into account, i guess i would use momentum of air hitting ball = momentum of ball (elastic collision) then use f=ma on the ball. This will give me the acceleration of the ball. But how do I use the acceleration of the ball upwards with gravity taken into account? This would mean the acceleration would be highest at the launch, be 0 somewhere midair, decrease to 9.8 m/s then stay there? Perhaps there is an easy equation that I am forgetting (I would never rule that out!)
Homework Equations
ummm.. that's what I am wondering..
if my first guess is right, then I use Ke= 1/2 m v2,
if my second guess is right , then I use Newton's 3rd.
The Attempt at a Solution
Please read part 1.
Thanks for your help.
P.S. If possible use metric units- I am Grade 11 Australia.