The trickiest part to this, as it turns out, is figuring out how to heat the pies
efficiently on a conveyor belt. What we have is a setup where pies enter the oven
on a circular conveyor, spent one minute in the oven, and then leave, cooked (in
theory) to perfection.
We want to run the conveyor belt quickly in order to make our pie-cooking
efficient and minimize the number of times each pie has to be baked. The issue,
of course, is that if we run the conveyor too quickly, there won't be enough time
for the steam to vent out, and the pies will explode. We've determined that this
happens if the pies ever heat faster than 2000. We're trying to figure out at
what rate w to turn the conveyor, in revolutions per minute (rpm).
(a) (1 point) The temperature in the oven T, in degrees C, is a function of
position (x, y) in meters relative to the center of the conveyor circle:
T(x,y) = 20 +500y²
Compute the gradient VT(z,y)./n(b) (2 points) The position (x,y) of a pie traveling clockwise along the conveyor
can be given as a function of the time t in minutes:
z(t) == cos(2mwt)
y(t) = sin(2mwt)
where 0 ≤t≤ Note that the bounds depend on the rotation rate w,
but we don't need to worry about that.
What is the velocity (z'(t), y(t))? That is to say, compute the deriva-
tives of and y with respect to t.
(c) (2 points) Using the chain rule, what is the derivative of temperature
with respect to time? (You should assume w is a constant.)
(d) (3 points) What is the maximum value of this expression, and what
is the smallest positive t for which it occurs? HINT: Use the fact
3/nthat sin(20) = 2 sin(8) cos(8), along with what you know about the graph
of the sine function.
(e) (1 point) As mentioned, we need to keep at or below 2000. What is
the highest value of that guarantees this? Leave your answer in exact
form.
(f) (2 points) After implementing the above, it's a quiet Tuesday at the factory,
until someone spills pie grease all over the conveyor! The conveyor is now
very slippery. You consult a mechanical engineer, who tells you that pies will
begin flying off the conveyor if they are ever moved with a total acceleration
exceeding 9m/s². Compute the acceleration vector (r"(t), y" (t))./n(g) (1 point) What is the magnitude a of the acceleration vector? As a
reminder, magnitude is equal to the square root of the sum of the squares
of the components.
(h) (1 point) So given the pie grease, what is the highest value of that
will prevent slippage? Again, leave your answer in exact form.
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