Calculus

Arc Length and Surface Area

Arc Length and Surface Area: Level 3 Challenges

Lise jogs along the curve defined by f ( x ) = 2 ( x 1 ) 3 2 3 f(x) =\dfrac{2(x - 1)^{\frac{3}{2}}}{3} from ( 1 , f ( 1 ) ) (1, f(1)) to ( 4 , f ( 4 ) ) . (4, f(4)). Steve jogs along the straight line connecting those two points. Steve and Lise both start from x = 1 x = 1 at the same time and Lise jogs at a speed of 7 3 units/s \frac{7}{\sqrt{3}} \mbox{ units}\mbox{/s} . What is the speed at which Steve must run (in units/s \mbox{ units}\mbox{/s} ) so that he arrives at ( 4 , f ( 4 ) ) (4, f(4)) at the same time as Lise?

的coordinates of a dot P P moving in the x y xy plane at time t t are given by: x = 5 e t cos t x = 5e^{-t}\cos t and y = 5 e t sin t y = 5e^{-t} \sin t . Let L a L_a be the distance traveled by P P in the interval 0 t a 0 \leq t \leq a . If lim a L a = z \displaystyle \lim_{a \to \infty} L_a = z , what is the value of z 2 z^2 ?

A delivery drone flying at constant speed 15 m/s 15 \text{ m/s} and constant height 2700 m 2700 \text{ m} toward a destination drops its goods. If the trajectory of the falling goods until it hits the ground can be described by the equation y = 2700 x 2 75 , y=2700-\frac{x^2}{75}, where x x is the horizontal distance it travels and y y 离地面的高度,是什么distance(not horizontal displacement) traveled by the goods until it hits the ground?

Note:You can use a 2 + u 2 d u = u 2 a 2 + u 2 + a 2 2 ln ( u + a 2 + u 2 ) + C . \displaystyle \int \sqrt{a^2+u^2}\,du=\frac{u}{2}\sqrt{a^2+u^2}+\frac{a^2}{2}\ln(u+\sqrt{a^2+u^2})+C.

的re exists a unique, positive-valued, non-constant, continuous and differentiable function y = f ( x ) y = f(x) such that

(i) over any specified interval, the area between f ( x ) f(x) and the x x -axis is equal to the arclength of the curve, and

(ii) f ( 0 ) = 1 f(0) = 1 .

If S = 1 2 f ( x ) d x S = \displaystyle\int_{-1}^{2} f(x) dx , then find 1000 S \lfloor 1000S \rfloor .

Consider the curve y = e x y={ e }^{ -x } in the first quadrant. Now it's rotated about the x -axis x\text{-axis} to obtain a solid of revolution. What is its surface area to 4 decimal places?

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