Math Problem Statement

A father is helping his young son learn to ride a bike by pushing on the bike seat from the back. At one point, the wheel of the bike is turning with an angular speed of one revolution in 6 seconds. Later, after 22.7 seconds have elapsed, it is turning with an angular speed of 18 revolutions per minute.

What angle did the wheel turn over these 22.7 seconds?

Solution

We are given the following information:

  • The initial angular speed of the bike's wheel is ω0=1revolution6seconds\omega_0 = \frac{1 \, \text{revolution}}{6 \, \text{seconds}}.
  • The final angular speed of the bike's wheel is ωf=18revolutions per minute\omega_f = 18 \, \text{revolutions per minute}.
  • The time interval during which this change occurs is t=22.7secondst = 22.7 \, \text{seconds}.

We want to determine the angle θ\theta (in revolutions) that the wheel turns over this period.

Step 1: Convert all angular speeds to the same units.

  • The initial angular speed is already in revolutions per second: ω0=16revolutions per second.\omega_0 = \frac{1}{6} \, \text{revolutions per second}.
  • The final angular speed is given in revolutions per minute, so we convert it to revolutions per second: ωf=18revolutions60seconds=0.3revolutions per second.\omega_f = \frac{18 \, \text{revolutions}}{60 \, \text{seconds}} = 0.3 \, \text{revolutions per second}.

Step 2: Calculate the average angular speed.

The average angular speed over the time interval can be calculated as: ωavg=ω0+ωf2=16+0.32=0.1667+0.32=0.23335revolutions per second.\omega_{\text{avg}} = \frac{\omega_0 + \omega_f}{2} = \frac{\frac{1}{6} + 0.3}{2} = \frac{0.1667 + 0.3}{2} = 0.23335 \, \text{revolutions per second}.

Step 3: Calculate the angle turned.

The angle θ\theta turned by the wheel during the time interval t=22.7secondst = 22.7 \, \text{seconds} is given by: θ=ωavgt=0.23335×22.7=5.299revolutions.\theta = \omega_{\text{avg}} \cdot t = 0.23335 \times 22.7 = 5.299 \, \text{revolutions}.

Thus, the wheel turns through an angle of approximately 5.30 revolutions over the 22.7 seconds.


Would you like more details on the calculation, or do you have any specific questions?

Here are 5 related questions to deepen understanding:

  1. How would the result change if the time interval was doubled?
  2. What if the final angular speed was 25 revolutions per minute instead?
  3. How does the average angular speed relate to the angular acceleration?
  4. Can you find the total number of radians the wheel turns instead of revolutions?
  5. How does constant angular acceleration affect the angle turned?

Tip: When converting between units like minutes and seconds, always ensure that both angular speeds are expressed in the same units before calculating.

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Math Problem Analysis

Mathematical Concepts

Angular Motion
Kinematics
Unit Conversion

Formulas

ω_avg = (ω_0 + ω_f) / 2
θ = ω_avg * t
Unit conversion: revolutions per minute to revolutions per second

Theorems

Average angular velocity theorem

Suitable Grade Level

Grades 9-12