Friday, August 19, 2011

Physics Help, Projectile Motion Problem?

Always draw a picture, it helps. Set your origin where the ball is shot to simplify things. you know that the ball has to go 6m in the x-direction in t seconds. I t also has to go to a height (from where it starts) of 1.2m in t seconds. the third thing you know is that the angle is 60 degrees. so you have 3 equations that you can setup. first, from trigonometry you know that tan(60)=Voy/Vox (initial y velocity divided by initial x velocity)... this is the info you get from the angle of the shot. you also know that the x velocity is 6/t because there is no x acceleration. so x initial v= x final v, so you can combine the two previous equations so that Voy = (6/t)* tan(60). The final equation you know is that Y=1/2*a*t^2+ Voy*t+Yo which simplifies to Y=-4.905*t^2+ Voy*t. Substituting the combined equation into the last one(and inputting numbers), you get... 1.2=-4.905*t^2+6tan(60). you can now solve for t. with the equations previously discussed you should be able to get the velocity if you also use the pythagorean theorem.

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