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An auto race takes place on a circular track. A car completes one lap in a time of 18.9 s, with an average tangential speed of 42.6 m/s. Find (a) the average angular speed and (b) the radius of the track.

Short Answer

Expert verified
(a) The average angular speed is approximately 0.332 rad/s. (b) The radius of the track is approximately 128.3 m.

Step by step solution

01

Understand the Relationship Between Tangential Speed and Angular Speed

The average tangential speed \( v_t \) is related to the average angular speed \( \omega \) by the formula \( v_t = \omega r \), where \( r \) is the radius of the circular track. This formula can be rearranged to \( \omega = \frac{v_t}{r} \).
02

Determine the Angular Speed Formula

Since \( \omega = \frac{v_t}{r} \), and we know that one full lap corresponds to an angle of \( 2\pi \) radians, we can also find \( \omega \) using time for one lap: \( \omega = \frac{2\pi}{T} \), where \( T = 18.9 \) s is the time per lap.
03

Calculate the Average Angular Speed

Substitute \( T = 18.9 \) s into the formula to get the average angular speed: \[ \omega = \frac{2\pi}{18.9} \approx 0.332 \text{ rad/s}. \]
04

Use Tangential Speed to Find Radius

To find the radius \( r \), we use the tangential speed formula: \( v_t = 42.6 \) m/s. Rearranging the equation for radius gives: \[ r = \frac{v_t}{\omega} = \frac{42.6}{0.332} \approx 128.3 \text{ m}. \]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Tangential Speed
Tangential speed is a pivotal concept when talking about objects moving in circular paths, such as cars on a racetrack. This is essentially how fast the car is moving along the circular path. It can be thought of as the speed you would observe if you could "unroll" the circular path into a straight line.At its core, tangential speed defines a measure of linear velocity as applied to circular motion. It has the same units as any linear speed value, which is meters per second (m/s). However, it鈥檚 important to note this is directionally specific to the circular path.
  • When discussing tangential speed, you're dealing with a speed that varies depending on the distance from the axis of rotation.
  • If two cars are moving on concentric circular tracks at the same angular speed, the car on the outer track travels faster in terms of tangential speed.
If you're solving problems involving tangential speed, remember the basic equation: \[ v_t = rac{2 ext{蟺}r}{T} \]where:
  • \( v_t \) is the tangential speed,
  • \( r \) is the radius of the circle, and
  • \( T \) is the time taken for one complete rotation.
Angular Speed
Angular speed is all about how quickly something is rotating. It tells us the rate at which an object moves around the center of a circle or any circular path. In terms of units, we often express angular speed in radians per second (rad/s), which measures how much of an arc (in radians) is covered per unit of time.The equation to calculate angular speed \( \omega \) is often given as:\[ \omega = \frac{2蟺}{T} \]where \( T \) is the period鈥攊.e., the time it takes to complete one full circle. This makes it pretty straightforward to calculate if you know the period.
  • A higher angular speed indicates a faster rotation.
  • Unlike linear speed, angular speed remains the same regardless of how large or small the circle is, provided the rotation period remains constant.
This concept is vital in understand motion dynamics in rotational settings, providing insight into how different parts of a rotating body relate to each other.
Radius of Circular Track
The radius of a circular track is a crucial aspect when dealing with circular motion because it essentially defines the size of the circle that the object travels around. In practical scenarios, like races, the radius directly influences the car's tangential speed.In the case of a car moving on a circular track, the radius \( r \) can be derived from rearranging the basic relationship between tangential speed \( v_t \) and angular speed \( \omega \):\[ r = \frac{v_t}{\omega} \]This equation shows us that:
  • If the tangential speed is known, the radius can be computed by knowing the angular speed.
  • Similarly, the formula showcases how angular and tangential speeds are interconnected through the radius.
If the track is larger (greater radius), the same angular speed will result in larger tangential speed values. This relationship is foundational in physics, especially in mechanics dealing with rotational motion and dynamics.

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Most popular questions from this chapter

The differential gear of a car axle allows the wheel on the left side of a car to rotate at a different angular speed than the wheel on the right side. A car is driving at a constant speed around a circular track on level ground, completing each lap in 19.5 s. The distance between the tires on the left and right sides of the car is 1.60 m, and the radius of each wheel is 0.350 m. What is the difference between the angular speeds of the wheels on the left and right sides of the car?

Two Formula One racing cars are negotiating a circular turn, and they have the same centripetal acceleration. However, the path of car A has a radius of 48 m, while that of car B is 36 m. Determine the ratio of the angular speed of car A to the angular speed of car B.

A string trimmer is a tool for cutting grass and weeds; it utilizes a length of nylon 鈥渟tring鈥 that rotates about an axis perpendicular to one end of the string. The string rotates at an angular speed of 47 rev/s, and its tip has a tangential speed of 54 m/s. What is the length of the rotating string?

A car is traveling along a road, and its engine is turning over with an angular velocity of 220 rad/s. The driver steps on the accelerator, and in a time of 10.0 s the angular velocity increases to 280 rad/s. (a) What would have been the angular displacement of the engine if its angular velocity had remained constant at the initial value of 220 rad/s during the entire 10.0-s interval? (b) What would have been the angular displacement if the angular velocity had been equal to its final value of 280 rad/s during the entire 10.0-s interval? (c) Determine the actual value of the angular displacement during the 10.0-s interval.

The earth spins on its axis once a day and orbits the sun once a year \(\left(365_{4}^{1} \text { days). Determine the average angular velocity (in rad/s) of the }\right.\) earth as it \((\text { a) spins on its axis and }(b) \text { orbits the sun. In each case, }\) take the positive direction for the angular displacement to be the direction of the earth's motion.

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