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(a) What angle in radians is subtended by an arc 1.50 m long on the circumference of a circle of radius 2.50 m? What is this angle in degrees? (b) An arc 14.0 cm long on the circumference of a circle subtends an angle of 128 \(^\circ\). What is the radius of the circle? (c) The angle between two radii of a circle with radius 1.50 m is 0.700 rad. What length of arc is intercepted on the circumference of the circle by the two radii?

Short Answer

Expert verified
(a) 0.60 rad, 34.38°; (b) Radius = 6.27 cm; (c) Arc length = 1.05 m.

Step by step solution

01

Calculate Radian Measure from Arc Length and Radius

To find the radian measure \( \theta \) subtended by an arc on a circle, the formula is \( \theta = \frac{s}{r} \) where \( s \) is the arc length and \( r \) is the radius of the circle. For the given arc length of 1.50 m and radius of 2.50 m, apply the formula: \[ \theta = \frac{1.50}{2.50} = 0.60 \text{ radians} \]
02

Convert Radians to Degrees

To convert an angle from radians to degrees, use the conversion factor \( 180^\circ / \pi \). Therefore, the angle in degrees is: \[ 0.60 \times \frac{180}{\pi} \approx 34.38^\circ \]
03

Calculate Circle Radius from Arc Length and Angle

For the arc length \( s = 14.0 \text{ cm} \) and angle \( 128^\circ \), first convert the angle to radians: \[ 128^\circ \times \frac{\pi}{180} \approx 2.234 \text{ radians} \] Then, rearrange the formula \( \theta = \frac{s}{r} \) to solve for \( r \): \[ r = \frac{s}{\theta} = \frac{14.0}{2.234} \approx 6.27 \text{ cm} \]
04

Calculate Arc Length from Angle and Radius

With a radius of 1.50 m and an angle of 0.700 rad, apply the formula \( s = r \times \theta \) to find the arc length: \[ s = 1.50 \times 0.700 = 1.05 \text{ m} \]

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Key Concepts

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

Understanding Arc Length
Arc length is a portion of a circle's circumference. Imagine walking along the edge of a circle, the path you cover is the arc length. It's a central concept in geometry. Understanding the relationship between the arc length, circle radius, and angle is essential.
  • Formula: To find an angle in radians using arc length, use the formula \( \theta = \frac{s}{r} \), where \( s \) is the arc length and \( r \) is the radius.
  • Example: If you have an arc of 1.5 meters along a circle with a radius of 2.5 meters, apply the formula to get \( \theta = \frac{1.50}{2.50} = 0.60 \) radians.
For clarity, always remember that you need the arc and radius to calculate angles in radians. This helps in various applications, including converting into degrees.
Circle Radius and Its Importance
The radius is the distance from the center of the circle to any point along its edge. It provides a measure of the circle's size and is pivotal in calculating other geometric properties like arc length and angles.
  • Determining Radius: When given an arc length and angle, you can find the circle radius by rearranging the formula \( \theta = \frac{s}{r} \) to \( r = \frac{s}{\theta} \).
  • Example: Suppose an arc is 14 cm long and subtends an angle of 128 degrees. First, convert 128 degrees to radians (\( 128 \times \frac{\pi}{180} \approx 2.234 \) radians), then find the radius: \( r = \frac{14.0}{2.234} \approx 6.27 \) cm.
Using the radius, you can derive critical information about the circle, be it to find the circumference or, as in this context, solve for unknown properties from known ones.
Angle Conversion: Radians to Degrees
Converting angles from radians to degrees, and vice versa, is a basic yet crucial operation. Understanding this conversion helps in bridging problems that require visualizing angles.
  • Conversion Formula: To convert radians to degrees, multiply the radian value by \( \frac{180}{\pi} \).
  • Example: For an angle of 0.60 radians, you find degrees by: \( 0.60 \times \frac{180}{\pi} \approx 34.38^{\circ} \).
The ability to switch between radians and degrees allows ease of solving diverse problems in mathematics and physics. It’s vital when working through problems involving circular motion, such as calculating revolutions, where these conversions turn out handy.

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Most popular questions from this chapter

A thin, light wire is wrapped around the rim of a wheel as shown in Fig. E9.45. The wheel rotates about a stationary horizontal axle that passes through the center of the wheel. The wheel has radius 0.180 m and moment of inertia for rotation about the axle of \(I =\) 0.480 kg \(\cdot\) m\(^2\). A small block with mass 0.340 kg is suspended from the free end of the wire. When the system is released from rest, the block descends with constant acceleration. The bearings in the wheel at the axle are rusty, so friction there does \(-\)9.00 J of work as the block descends 3.00 m. What is the magnitude of the angular velocity of the wheel after the block has descended 3.00 m?

The rotating blade of a blender turns with constant angular acceleration 1.50 rad/s\(^2\). (a) How much time does it take to reach an angular velocity of 36.0 rad/s, starting from rest? (b) Through how many revolutions does the blade turn in this time interval?

A uniform 2.00-m ladder of mass 9.00 kg is leaning against a vertical wall while making an angle of 53.0\(^\circ\) with the floor. A worker pushes the ladder up against the wall until it is vertical. What is the increase in the gravitational potential energy of the ladder?

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A bicycle wheel has an initial angular velocity of 1.50 rad/s. (a) If its angular acceleration is constant and equal to 0.200 rad/s\(^2\), what is its angular velocity at \(t =\) 2.50 s? (b) Through what angle has the wheel turned between \(t =\) 0 and \(t =\) 2.50 s?

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