HG2M13
________________________________________________________________________
Problem Sheet 1
Additional Questions
1.
If = 2 xz 4 x 2 y , find and || at the point (2, -2, -1).
2.
If A = 2 x 2 i 3 yzj + xz 2 k and = 2z x3y, find A and A at the
point (1, -1, 1).
3.
If F = x 2 z + e y
and G = 2 z 2 y xy 2 , find
i.
(F - G)
at the point (1, 0, -2).
ii.
(FG)
4.
Find |r|3
5.
Prove that
i.
(F + G) = F + G
ii.
(FG) = F G + G F
where F and G are differentiable scalar functions of x, y and z.
6.
Find the directional derivative of = x 2 yz + 4 xz 2 at (1, -2, -1) in the
direction of 2i j 2k.
7.
Find the direction vector where f ( x, y , z ) = xyz 3 y 2 increases most rapidly
at the point (1, 1, 3) and also the maximum rate of change of f .
8.
Find a vector that is normal to the level curve xy 2 3 x 2 y = 10 at the point
(1, 5) .
9.
Determine the unit normal vector to the surface xz 2 3 xyz 7 x = 2 at the
point (1, 0, 3) .
10.
If A = 3 xyz 2 i + 2 xy 3 j x 2 yz k and = 3 x 2 yz , find
i. A
iv. ()
at the point (1, -1, 1).
ii. A
v. A
iii. (A)
11.
If = 3 x 2 z y 2 z 3 + 4 x 3 y + 2 x 3 y 5 , find 2 .
12.
Verify
that
the
vector
field
F( x, y, z ) = ( y sin z ) i + xz j + xe y k
incompressible.
_____________________________________________________________________ 1
is
HG2M13
________________________________________________________________________
13.
Is the vector field F( x, y , z ) = ( ze x + sin y )i + ( x cos y ) j + e x k irrotational?
Explain.
14.
Verify that the vector field F( x, y , z ) = (e y + yz ) i + ( xe y + xz ) j + ( xy 3) k is
conservative and find its potential function.
15.
Find
the
values
of
a and b such that the
F ( x, y, z ) = (4 xy + ayz ) i + (2 x 2 + 3 xz ) j + bxy k is irrotational.
vector
field
16.
Let A = A ( x, y, z ), B = B( x, y, z ) and = ( x, y, z ) . Assuming all derivatives
involved exist and are continuous, prove that
i.
(A + B) = A + B
ii.
(A) = () A + ( A)
17.
If A = 2 xz 2 i yzj + 3 xz 3 k and = x 2 yz , find
ii. curl (A)
i. A
v. curl grad (A)
at the point (1, 1, 1).
iii. ( A)
iv. [A curl A]
Answers
1. 10i 4j 16k, 2 93
2. 5, 7i j 11k
3. i. -4i + 9j + k
ii. -8j
4. 3rr
6. 37/3
8.
9.
5i + 7 j
10. i. 4
n =
ii. -15
11.
6 z + 24 xy 2 z 3 6 y 2 z
15.
a = 3, b = 3
17.
i. i + j
7.
3i 3 j + k ;
19
1
(2i 9 j + 6k )
11
iii. 1
iv. 6
14.
v.
i 8 j 5k
f ( x, y, z ) = xe y + xyz 3 z
ii. 5i 3j 4k
iii. 5i + 3k
iv.
-2i + j + 8k
v. 0
_____________________________________________________________________ 2