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    Image Projection

    "A 35 mm slide (picture actually 24*36 mm) is to be projected on a screen 1.8*2.7 m placed 9 m from the projector. What focal length lens should be used if the imageis to cover the screen?" I was trying to do this problem using the formula (1/do)+(1/di)=(1/f), but hten i realized i dont have...
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    I can't figure it out

    I have this trig identity problem i need to solve cos2x=cosx I have to find all the values of x, and i know the answer is x=0°+120°, but i can figure ou how. I've tried it over and over and my answer turns out to x=0°=180°. Please help, thank you.:uhh:
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    Box Promblem

    I really don't undersand the friction chapter in my physics book, can somebody please help with one question. "Two crates of a mas of 75 and 110 kg are at rest on a horizontal surface. A 730 N force is exerted on the 75 kg box. If the coeff. of kinetic friction is .15 what is the acceleration of...
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    Whats the force of this baseball?

    This is a simple problem, but for some reason i can't come up wit the answer. Im i using the wrong formula? A base ball is traveling and strikes a catchers mitt, bringing it to rest. the mitt recoils 11 cm. m=.14 kg vi=45 m/s vf=0 m/s d=11cm (.11 m) i used the formula vf^2=vi^2+2ad to get...
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    Friction in tires

    I can't figure this problem out. There doesn't seem to be enough information, but its in my school physics book so if someone could help id really apreciate it. "Drag car tires in contact with an asphalt surface probaby have the highest coefficients of static friction in the everyday world...
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    Max and min forces on an elevator.

    " A elevator with a mass of 4850 kg is to be designed so that the maximum acceleration is 0.0600 g's. What are the max and min forces the motor should exert on the cable?" I converted the .0600 gs to .558 m/s/s, but when iplugged it in to the F=ma formula i got the wrong answer? am i supposed...
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    Rocket balloon in a parrallel line

    Our teacher just gave us a priject to complete and i cannot figure it out. first of all we have limited supplies. we can use 5 ballons, 6 straws, 10 paperclips, 5 rubberbands, a whole roll of masking tape, scissors and a guide wire that cannot be altered. Our goal is to get the a balloon to go...
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    Rocket balloon, HElp

    Rocket ballon with gravitaion????? Our teacher just gave us a priject to complete and i cannot figure it out. :grumpy: first of all we have limited supplies. we can use 5 ballons, 6 straws, 10 paperclips, 5 rubberbands, a whole roll of masking tape, scissors and a guide wire that cannot be...
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