MP

chem 150

Overview of Derivatives and Their Applications

Derivative of Arcsine Function

  • Chain Rule Usage: The derivative of the function arcsin(3x) involves applying the chain rule.

    • The basic derivative formula is:
      \frac{d}{dx}(\text{arcsin}(x)) = \frac{1}{\sqrt{1 - x^2}}

    • Under the chain rule, if the input is not just x but rather 3x, we need to apply the rule as follows:

    • The derivative of arcsin(3x) becomes:
      \frac{1}{\sqrt{1 - (3x)^2}} \cdot \frac{d}{dx}(3x)

    • This results in:
      \frac{3}{\sqrt{1 - 9x^2}}

    • Implication: Multiply the outer function's derivative by the derivative of the inside function (3).

Transition to Higher Order Derivatives

  • The focus shifts to sections 3.4 and 3.5, focusing on:

    • Rates of change.

    • Applications, particularly concerning motion problems, such as projectile motion.

    • Importance of understanding first and second derivatives to analyze function behavior.

  • Concept of Higher Order Derivatives:

    • Higher order derivatives, such as the fourth and subsequent derivatives, can reveal patterns in functions;

    • Example: Derivatives of sine function exhibit a cyclical pattern every four derivatives.

Notation for Higher Order Derivatives

  1. Prime Notation:

    • For first, second, and third derivatives use:

      • f'(x), f''(x), f'''(x) respectively.

    • Beyond the third derivative, we use:

      • f^(n)(x) for the n-th derivative.

  2. Leibniz Notation:

    • Can also be expressed as:

      • \frac{d^n}{dx^n} for the n-th derivative.

  3. Example Function:

    • Generally, for f(x) = x^2 + 3ln(x):

      • f' = 2x + \frac{3}{x}

      • f'' = 2 - \frac{3}{x^2}

      • f''' = \frac{6}{x^3}

Projectile Motion and Acceleration

  • When modeling a projectile influenced only by gravity:

    • Acceleration: Constant at:

    • -a = -9.8 \, \text{m/s}^2 or -32 \, \text{ft/s}^2

  • Height Function:

    • The general model for height, given constant acceleration, is a quadratic polynomial:

      • h(t) = pt^2 + qt + r where:

      • p varies based on gravitational acceleration, and is negative if the motion is downward.

      • q = initial velocity (v₀).

      • r = initial height (h₀).

  • Deriving velocity and acceleration from the height function:

    • Velocity can be derived as:

    • v(t) = h'(t) = 2pt + q

    • Acceleration is derived as:

    • a(t) = v'(t) = h''(t) = 2p

Calculating Initial Values

  • To derive initial velocity and height using a specific height function:

    • Example: for height function h(t) = 24 + 40t - 16t², we analyze:

      • At t=0, h(0) = 24 (initial height).

      • Finding Initial Velocity: Use the first derivative, yielding 40 ft/s.

Time to Reach Ground and Velocity at Impact

  • To determine when a projectile strikes the ground, set the height equation to zero:

    • Solve quadratic equations to find time.

  • Velocity upon impact can be calculated using the derivative of the height function and plugging in the time found_.

Maximum Height

  • The maximum height is found when the velocity function equals zero, indicating that the directed motion has ceased to ascend and is about to descend.

  • This can also be done using the vertex formula for quadratics, identifying the peak of a parabola.

Application Scenarios

  • Consider objects falling purely under gravitational influence:

    • The outcome involves recognizing constant acceleration leading to behaviors that can be predicted from the polynomial nature of the governing equations.

  • Example Scenario with a Falling Piano:

    • Using similar quadratic characteristics, determine the ground impact behavior and the effects of constant acceleration on height and velocity profiles.

Patterns and Higher Derivatives Overview

  • The derivative behavior elucidates broader mathematical implications:

    • For any polynomial higher than its degree, derivatives continuously lead to zero.

    • Connections to continuous motion and acceleration provide substantive insight throughout calculus.

Relationship of Derivatives to Function Behavior

  • Increasing/decreasing intervals are established through the first derivative:

    • If f'(x) > 0, f increases;

    • If f'(x) < 0, f decreases.

  • In contrast, concavity is determined using second derivatives:

    • If f''(x) > 0, function is concave up;

    • If f''(x) < 0, function is concave down.

Graphical Representation of Derivatives

  • Visual assessment includes observing tangent slopes and concavity to identify increasing/decreasing behavior alongside their concavity.

  • A negative slope in f indicates a downward motion, leading to corresponding downward movements in derivatives reflecting these rates of change.