# Misc 3 - Chapter 10 Class 12 Vector Algebra

Last updated at Dec. 19, 2018 by Teachoo

Last updated at Dec. 19, 2018 by Teachoo

Transcript

Misc 3 A girl walks 4 km towards west, then she walks 3 km in a direction 30ยฐ east of north and stops. Determine the girlโs displacement from her initial point of departure. Let initial point of departure be O(0, 0) & OA = 4km AB = 3km โ XAB = 30ยฐ Here, Displacement will be vector (๐๐ต) โ So, we need to find coordinates of B Now, โ BAO = 90ยฐ โ โ XAB = 90ยฐ โ 30ยฐ = 60ยฐ Let us draw BD โฅ OA In right triangle ADB sin 60ยฐ = ๐ต๐ท/๐ด๐ต โ3/2 = ๐ต๐ท/3 (3โ3)/2 = BD BD = (๐โ๐)/๐ In right triangle ADB cos 60ยฐ = ๐ด๐ท/๐ด๐ต 1/2 = ๐ด๐ท/3 3/2 = AD AD = ๐/๐ Now, OD = OA โ AD OD = 4 โ ๐/๐ = (๐(๐) โ ๐)/๐ = ๐/๐ So, x-coordinate of point B = โOD = (โ๐)/๐ y-coordinate of point B = BD = (๐โ๐)/๐ Thus, coordinates of point B = ((โ๐)/๐, (๐โ๐)/๐) So, Displacement = (โ๐)/๐ ๐ ฬ + (๐โ๐)/๐ ๐ ฬ

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.