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PHYS1150 Problem Solving in Physics

Assignment 6

Due Date: November 26, 2022 at 11:00 pm

The problems in this paper have a wide range of difficulties.  They are specially designed to strengthen students’ concepts and to develop the problem solving skills.  Students are expected to drill the prob- lems with perseverance.

1. If u = tan1   ^  ^, find  and夕(u) . Verify that z  + 夕(u) =  sin 2u.

,z               ,2 z

3.   (a) If f (zo 夕) = 0 and 9(o 之) = 0, show that

1  ,2  (b) If a2 z2 + b2 2  = c2 2 , show that

,f ,9 d       ,f ,9

,夕 ,之 dz     ,z ,夕 .

1  ,2        1 

b2  ,夕2         c2 .

(8 marks)

(8 marks) (8 marks)

(8 marks)

4.  Given that u(zo 夕) and u(zo 夕) are differentiable functions, where z = r cos y and = r sin y .

Show that the equation set

(12 marks)

.(.)           =

(*)

 ,夕   =

becomes

,u

,夕

,u

,z

,u          1 ,u

.(.)    ,u              1 ,u

5.  Given that u(zo 夕) is a differentiable function, where z = r cos y and  = r sin y . Show that   (12 marks)

,2u     ,2u      ,2u     1 ,u     1  ,2u

,z2        ,夕2         ,r2        r ,r     r2  ,y2

6.  Given that u(zo 夕) and u(zo 夕) are differentiable functions. Show that                      (12 marks)

+            = 1         and

,u ,z      ,u ,夕

,z ,u     ,夕 ,u

7.  Given that  = f  o r 2 a(.)s, where a is a constant. Let z =  and  = r 2 a(.)s .           (a)  Show that r(之) =   +   夕(f)  and s(之) =     夕(f).                      (8 marks)

(b)  Show further that r(2)2(之)  +s(2)2(之)  =   +   夕(2)f2.                                        (8 marks)

8.   (a) If (zo 夕) is a homogeneous function of degree 2, i.e. = z2 f z(夕), show that  (8 marks)

z z(之) + 夕(之) = 2        and        z2(之)  + 2 z夕 ,夕 + 2夕(2)2(之)  = 2                 (b) If u = ln z(z)2(4) + 夕(夕)2(4), find z  + 夕(u) and z2   + 2 z夕 ,2 + 2夕(2)u2 .        (8 marks)