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Parametric, Polar & Vector Motion Lab

Trace parametric curves, shade polar regions, and decompose vector-valued motion into velocity and acceleration. Switch between three modes to see how different coordinate systems reveal different properties of curves and motion.

Guided Experiment Parametric Motion Analysis

How does the velocity vector change along a cycloid? Is the speed constant?

Write your hypothesis in the Lab Report panel, then click Next.

Controls

Results

Position(1.0000, 0.0000)
dx/dt0.0000
dy/dt1.0000
dy/dx
Speed |v|1.0000
Arc Length0.0000

Graph

Velocity

Data Table

(0 rows)
#TrialModePresett / θPositionDerivative / SlopeSpeed / Area / κ
0 / 500
0 / 500
0 / 500

Reference Guide

Parametric Derivatives

For a curve defined by x(t) and y(t), the slope is found using the chain rule.

dydx=dy/dtdx/dt\frac{dy}{dx} = \frac{dy/dt}{dx/dt}

Arc length is the integral of the speed function.

L=∫ab(dxdt)2+(dydt)2 dtL = \int_a^b \sqrt{\left(\frac{dx}{dt}\right)^2 + \left(\frac{dy}{dt}\right)^2}\, dt

Polar Area

The area enclosed by a polar curve between two angles is given by the following integral.

A=12∫αβr2 dθA = \frac{1}{2}\int_{\alpha}^{\beta} r^2\, d\theta

This formula sweeps out infinitesimal triangular sectors from the origin. The factor of 1/2 comes from the area of each triangle with base r and infinitesimal angle dθ.

Polar Slope

The slope of a polar curve in Cartesian coordinates requires converting derivatives.

dydx=drdθsin⁡θ+rcos⁡θdrdθcos⁡θ−rsin⁡θ\frac{dy}{dx} = \frac{\frac{dr}{d\theta}\sin\theta + r\cos\theta}{\frac{dr}{d\theta}\cos\theta - r\sin\theta}

This comes from x = r cos θ and y = r sin θ with the product rule.

Vector Calculus

For a vector-valued function r(t), velocity and acceleration decompose into tangential and normal components.

κ=∣v×a∣∣v∣3,aT=v⋅a∣v∣,aN=∣a∣2−aT2\kappa = \frac{|\mathbf{v} \times \mathbf{a}|}{|\mathbf{v}|^3}, \quad a_T = \frac{\mathbf{v} \cdot \mathbf{a}}{|\mathbf{v}|}, \quad a_N = \sqrt{|\mathbf{a}|^2 - a_T^2}

Curvature κ measures how quickly the direction of velocity changes. Tangential acceleration changes the speed, while normal acceleration changes the direction.

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