Math Problem Statement

A rod of 8 cm is attached at one end to a rotating wheel of radius 4 cm. The wheel rotates counterclockwise at 2 revolutions per second, and the other end of the rod moves along a horizontal bar. Given the setup, calculate various properties such as coordinates of specific points at t = 1/12 sec, angular velocity, and functions for coordinates of points as a function of time.

Solution

Let’s go through the problem step by step. Here’s an analysis and solution for each part of the problem:

Given Information:

  • A rod of length 8 cm is attached at one end (Point AA) to a wheel of radius 4 cm.
  • The wheel rotates counterclockwise at 2.02.0 revolutions per second (rps), and its center is at the origin.
  • The other end of the rod (Point BB) can move along a horizontal line.

The time t=0t = 0 represents the initial position of the rod, and at t=112t = \frac{1}{12} sec, the rod is shown rotated to a new position.

(a) Coordinates of Points AA and BB at t=112t = \frac{1}{12} sec

From the solution provided:

  • Point AA at t=112t = \frac{1}{12} sec has coordinates (2,23)\left( 2, 2\sqrt{3} \right).
  • Point BB has coordinates (2+213,0)\left( 2 + 2\sqrt{13}, 0 \right).

These are correct based on the given rotations and lengths.

(b) Angular Velocity ω\omega of Point AA

Since the wheel rotates at 2.02.0 rps:

  1. Convert revolutions per second to radians per second: ω=2×2π=4π radians per second\omega = 2 \times 2\pi = 4\pi \text{ radians per second}

(c) Coordinates of Point AA as a Function of tt

The coordinates of AA on the wheel will follow a circular path, so we can express its position as: xA=4cos(4πt)x_A = 4 \cos(4\pi t) yA=4sin(4πt)y_A = 4 \sin(4\pi t)

(d) X-Coordinate of Point BB as a Function of tt

Since BB is at a fixed distance of 8 cm from AA, its position along the x-axis will depend on the rotation of AA:

  1. Find the x-coordinate by projecting point BB along the line that is 8 cm away from AA: xB=xA+8cos(4πt)=4cos(4πt)+8cos(4πt)x_B = x_A + 8 \cos(4\pi t) = 4 \cos(4\pi t) + 8 \cos(4\pi t)

Would you like further details on any step?

Follow-up Questions:

  1. How would the solution change if the wheel rotated clockwise?
  2. How does increasing the radius of the wheel affect the coordinates of points AA and BB?
  3. What if point BB could move vertically? How would this affect the function?
  4. What would be the angular velocity if the wheel rotated at 3 revolutions per second?
  5. Could you express the coordinates of point BB in polar form?

Tip:

Always convert rotational speed to radians per second when dealing with angular velocity in circular motion problems.

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Math Problem Analysis

Mathematical Concepts

Circular Motion
Angular Velocity
Coordinate Geometry
Trigonometric Functions

Formulas

Angular velocity formula: \( \omega = 2 \pi \times \text{revolutions per second} \)
Coordinate functions for circular motion: \( x = r \cos(\theta) \), \( y = r \sin(\theta) \)

Theorems

Trigonometric relationships in circular motion
Coordinate transformation in rotating systems

Suitable Grade Level

Grades 11-12