Math Problem Statement

The speed of a moving bullet can be determined by allowing the bullet to pass through two rotating paper disks mounted a distance 67 cm apart on the same axle. From the angular displacement 24.6° of the two bullet holes in the disks and the rotational speed 1350 rev/min of the disks, we can determine the speed of the bullet. What is the speed of the bullet? Answer in units of m/s.

Solution

We need to calculate the speed of the bullet based on the information given:

Key Information:

  • The distance between the two disks is d=67cm=0.67md = 67 \, \text{cm} = 0.67 \, \text{m}.
  • The angular displacement between the bullet holes is θ=24.6=24.6360revolutions\theta = 24.6^\circ = \frac{24.6}{360} \, \text{revolutions}.
  • The rotational speed of the disks is f=1350rev/minf = 1350 \, \text{rev/min}.

Steps to Solve:

  1. Convert angular displacement to time: The angular displacement corresponds to the time it took for the bullet to travel the distance between the disks. The time can be calculated using the rotational speed: t=angular displacementrotational speed.t = \frac{\text{angular displacement}}{\text{rotational speed}}. Converting 1350rev/min1350 \, \text{rev/min} to revolutions per second (rev/s\text{rev/s}): f=135060=22.5rev/s.f = \frac{1350}{60} = 22.5 \, \text{rev/s}. Therefore, the time is: t=θf=24.636022.5.t = \frac{\theta}{f} = \frac{\frac{24.6}{360}}{22.5}.

  2. Calculate the bullet speed: The speed of the bullet is given by: v=dt.v = \frac{d}{t}.

Let me calculate this step-by-step. Given data distance_m = 0.67 # distance between disks in meters angular_displacement_deg = 24.6 # angular displacement in degrees rotational_speed_rpm = 1350 # rotational speed in revolutions per minute

Convert angular displacement to revolutions

angular_displacement_rev = angular_displacement_deg / 360

Convert rotational speed to revolutions per second

rotational_speed_rps = rotational_speed_rpm / 60

Calculate time (t = angular displacement / rotational speed)

time_s = angular_displacement_rev / rotational_speed_rps

Calculate bullet speed (v = d / t)

bullet_speed_m_s = distance_m / time_s

bullet_speed_m_sThe speed of the bullet is approximately 220.61 m/s.

Explanation:

  1. The angular displacement of 24.624.6^\circ corresponds to the time it takes for the disks to rotate through that angle, given their rotational speed.
  2. Using the time and the distance between the disks, the speed of the bullet is calculated.

Would you like me to elaborate further or solve related problems? Here are 5 related questions:

  1. How does changing the rotational speed affect the accuracy of the measurement?
  2. What is the time taken by the bullet to travel the 67 cm distance?
  3. If the angular displacement were doubled, what would happen to the calculated speed of the bullet?
  4. How would the result change if the distance between the disks was increased to 1 meter?
  5. How can we improve the precision of such an experiment?

Tip: Always convert units to SI (meters, seconds) to avoid confusion in calculations!

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Math Problem Analysis

Mathematical Concepts

Kinematics
Angular Motion
Conversion between units (degrees to revolutions, RPM to RPS)
Time and velocity calculations

Formulas

t = angular displacement / rotational speed
v = d / t

Theorems

Relationship between linear and angular motion
Unit conversions in rotational motion

Suitable Grade Level

Grades 10-12