The temperature (in degrees Celsius) at a point x , y on a metal plate in the x y -plane is T x , y = x y 1 + x 2 + y 2 (a) Find the rate of change of temperature at 1 , 1 in the direction of a = 2 i − j . (b) An ant at 1 , 1 wants to walk in the direction in which the temperature drops most rapidly. Find a unit vector in that direction.
The temperature (in degrees Celsius) at a point x , y on a metal plate in the x y -plane is T x , y = x y 1 + x 2 + y 2 (a) Find the rate of change of temperature at 1 , 1 in the direction of a = 2 i − j . (b) An ant at 1 , 1 wants to walk in the direction in which the temperature drops most rapidly. Find a unit vector in that direction.
Find the maximum rate of change of f at the given point and the direction in which it occurs.
f(x, y) = 7xy2, (3, −5)
maximum rate of change
direction vector
The concentration of salt in a fluid at
is given by
mg/cm
. You are at the point
.
(a) In which direction should you move if you want the concentration to increase the fastest?
Direction:
(Give your answer as a vector.)
(b) You start to move in the direction you found in part (a) at a speed of
cm/sec. How fast is the concentration changing?
Rate of change =
HINT: The rate of change of the perceived concentration F(x,y,z), by the Chain Rule, equals the dot product of the gradient vector of F and the velocity of the "particle". To find it, we need to know the norms (magnitudes) of both vectors and the angle between them. In this problem the angle is known.
The position vector r describes the path of an object moving in the xy-plane.
Position Vector
Point
r(t) = 2 cos ti + 2 sin tj
(VZ, V2)
(a) Find the velocity vector, speed, and acceleration vector of the object.
v(t)
=
s(t)
a(t) =
(b) Evaluate the velocity vector and acceleration vector of the object at the given point.
a(#) =
Elementary Statistics: Picturing the World (7th Edition)
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