toki Posted December 25, 2015 Posted December 25, 2015 there is a lamppost which is 40 m high.5 m infront of the post there is a metal plate which is 8 m long. which angle of the plate with the verticle line will give the longest shadow?
imatfaal Posted December 25, 2015 Posted December 25, 2015 Moved to homework help please show your ideas and workings first - then members can show you right direction to take.
ajb Posted December 26, 2015 Posted December 26, 2015 My general suggestion to to sketch the set-up. That may help you see what to try. 1
kisai Posted December 26, 2015 Posted December 26, 2015 i dont have ANY idea how to start it. Have you taken any trigonometry yet?
toki Posted December 27, 2015 Author Posted December 27, 2015 Yes But how can I determine the maximum value using trigonometry? Plz help me with any clue
swansont Posted December 27, 2015 Posted December 27, 2015 Can you think of how there would be no shadow at all? That might help get you started.
toki Posted December 27, 2015 Author Posted December 27, 2015 Yeah ,when the sheet will make 0 or 180 degree with the lamp light,there will be no shadow.
swansont Posted December 27, 2015 Posted December 27, 2015 Yeah ,when the sheet will make 0 or 180 degree with the lamp light,there will be no shadow. So what angle is that with respect to the vertical line? And what condition will maximize a shadow? 1
toki Posted December 30, 2015 Author Posted December 30, 2015 So what angle is that with respect to the vertical line? And what condition will maximize a shadow? it is 7.125degree using trigonometry. and it is in the opposite position .that is -7.125 degree
swansont Posted December 30, 2015 Posted December 30, 2015 it is 7.125degree using trigonometry. and it is in the opposite position .that is -7.125 degree The negative of the angle isn't the opposite condition. What's the angle between the plate and the light beam that maximizes the shadow?
toki Posted December 30, 2015 Author Posted December 30, 2015 i cant get it.sorry. i also tried much to get this angle
Function Posted January 22, 2016 Posted January 22, 2016 (edited) 90°? Did I wrongly interpret the problem? (red = shadow; black = pole and plate (circle because of different angles, at least this is what I interpreted), yellow the light beam between post and plate when it's placed at about 45°, blue if it's placed at 0° with the vertical) I didn't calculate it, but shouldn't it be 45°? Edited January 22, 2016 by Function
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