What is the common angular speed…

Physics Questions

What is the common angular speed of both reels in a videotape cassette if the tape is 240 m long and plays for 2.1 hours, with the full reel having an outer radius of 47 mm and an inner radius of 11 mm?

Short Answer

The procedure involves understanding the given data, deriving the effective radius of the tape, calculating the linear speed, and eventually computing the angular speed. The final result indicates that both reels achieve an angular speed of approximately 0.930 rad/s.

Step-by-Step Solution

Step 1: Understand the Given Data

Start by reviewing the available data to comprehend the scenario fully. Key variables include:

  • Total Length of Tape: L = 240 m
  • Time Interval: t = 2.1 hours, which equals 7560 seconds
  • Outer Radius of Tape: ro = 47 mm
  • Inner Radius of Tape: ri = 11 mm

Step 2: Calculate the Effective Radius and Linear Speed

Next, you will calculate the effective radius and linear speed to find the angular speed. The effective radius (r) can be derived using:

  • Formula: r = ‚àö((ro2 + ri2)/2)
  • Calculated Effective Radius: r ≈ 0.03413 m
  • Linear Speed (v): v = L/t = 240 m / 7560 s = 0.0317 m/s

Step 3: Compute Angular Speed and Conclusion

Finally, you compute the angular speed (ω) using the values found earlier. The relationship between linear speed and angular speed is given by:

  • Angular Speed Formula: ω = r √ó v
  • Calculation: Substituting the values gives ω = 0.03413 m √ó 0.0317 m/s ≈ 0.930 rad/s
  • Conclusion: Both reels have the same angular speed of 0.930 rad/s during playback.

Related Concepts

Total length of tape

The overall measure of the tape’s length, in this case 240 meters, which plays a vital role in calculating linear speed.

Linear speed

The rate at which the tape is moving, calculated as the total length divided by the time interval, measured in meters per second (m/s).

Angular speed

The rate of rotation of the tape, expressing how quickly it is spinning in radians per second (rad/s), derived from the effective radius and linear speed.

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