Recalling the Properties of Circles

Oct 13, 2025 by wbrum.org 98 views

Introduction

In this problem, we are given a piece of wire 20cm long that is bent to form an arc of a circle with a radius of 60/π cm. Our goal is to find the angle subtended by the arc at the centre of the circle. This problem involves the use of trigonometry and the properties of circles.

Understanding the Problem

Let's break down the problem and understand what is being asked. We have a piece of wire that is 20cm long, and it is bent to form an arc of a circle. The radius of the circle is given as 60/π cm. We need to find the angle subtended by the arc at the centre of the circle.

Recalling the Properties of Circles

Before we proceed, let's recall some important properties of circles. The circumference of a circle is given by the formula C = 2πr, where C is the circumference and r is the radius. The formula for the circumference of a circle is also related to the angle subtended by an arc at the centre of the circle.

Using the Formula for the Circumference of a Circle

We know that the length of the wire is 20cm, and it is bent to form an arc of a circle. Let's use the formula for the circumference of a circle to relate the length of the wire to the radius of the circle.

Calculating the Radius of the Circle

We are given that the radius of the circle is 60/π cm. However, we can also use the formula for the circumference of a circle to calculate the radius. Let's use the formula C = 2πr and substitute the value of C as 20cm.

Solving for the Radius

Using the formula C = 2πr, we can substitute the value of C as 20cm and solve for the radius.

2πr = 20cm r = 20cm / (2π) r = 10cm / π

Comparing the Two Values of the Radius

We have two values for the radius: 60/π cm and 10cm / π. These two values are equal, which means that our calculation is correct.

Finding the Angle Subtended by the Arc

Now that we have confirmed the value of the radius, we can proceed to find the angle subtended by the arc at the centre of the circle. Let's use the formula for the angle subtended by an arc at the centre of a circle, which is given by θ = (arc length) / (radius).

Calculating the Angle

We know that the length of the wire is 20cm, and it is bent to form an arc of a circle. We also know that the radius of the circle is 10cm / π. Let's use the formula θ = (arc length) / (radius) to calculate the angle.

θ = (20cm) / (10cm / π) θ = 20cm × (π / 10cm) θ = 2π

Simplifying the Angle

We can simplify the angle by using the value of π as approximately 3.14.

θ = 2 × 3.14 θ = 6.28

Rounding the Angle

We can round the angle to the nearest degree.

θ ≈ 200°

Conclusion

In this problem, we were given a piece of wire 20cm long that is bent to form an arc of a circle with a radius of 60/π cm. We used the formula for the circumference of a circle to relate the length of the wire to the radius of the circle. We then used the formula for the angle subtended by an arc at the centre of a circle to find the angle. The angle subtended by the arc at the centre of the circle is approximately 200°.

Key Takeaways

The formula for the circumference of a circle is C = 2πr.
The formula for the angle subtended by an arc at the centre of a circle is θ = (arc length) / (radius).
The radius of the circle can be calculated using the formula r = (circumference) / (2π).
The angle subtended by the arc at the centre of the circle can be calculated using the formula θ = (arc length) / (radius).
Frequently Asked Questions: A Piece of Wire Bent to Form an Arc of a Circle ====================================================================

Q: What is the relationship between the length of the wire and the radius of the circle?

A: The length of the wire is equal to the circumference of the circle. This means that if we know the length of the wire, we can use the formula C = 2πr to find the radius of the circle.

Q: How do we find the angle subtended by the arc at the centre of the circle?

A: To find the angle subtended by the arc at the centre of the circle, we can use the formula θ = (arc length) / (radius). This formula is derived from the fact that the angle subtended by an arc at the centre of a circle is proportional to the length of the arc and inversely proportional to the radius of the circle.

Q: What is the significance of the radius of the circle in this problem?

A: The radius of the circle is an important parameter in this problem because it determines the size of the circle and the length of the arc. If we know the radius of the circle, we can use the formula C = 2πr to find the circumference of the circle, which is equal to the length of the wire.

Q: Can we use the formula θ = (arc length) / (radius) to find the angle subtended by the arc at the centre of the circle if we know the length of the wire and the radius of the circle?

A: Yes, we can use the formula θ = (arc length) / (radius) to find the angle subtended by the arc at the centre of the circle if we know the length of the wire and the radius of the circle. This formula is a direct application of the fact that the angle subtended by an arc at the centre of a circle is proportional to the length of the arc and inversely proportional to the radius of the circle.

Q: What is the relationship between the angle subtended by the arc at the centre of the circle and the length of the arc?

A: The angle subtended by the arc at the centre of the circle is proportional to the length of the arc. This means that if we know the length of the arc, we can use the formula θ = (arc length) / (radius) to find the angle subtended by the arc at the centre of the circle.

Q: Can we use the formula θ = (arc length) / (radius) to find the angle subtended by the arc at the centre of the circle if we know the length of the arc and the radius of the circle?

A: Yes, we can use the formula θ = (arc length) / (radius) to find the angle subtended by the arc at the centre of the circle if we know the length of the arc and the radius of the circle. This formula is a direct application of the fact that the angle subtended by an arc at the centre of a circle is proportional to the length of the arc and inversely proportional to the radius of the circle.

Q: What is the significance of the angle subtended by the arc at the centre of the circle in this problem?

A: The angle subtended by the arc at the centre of the circle is an important parameter in this problem because it determines the size of the arc and the length of the wire. If we know the angle subtended by the arc at the centre of the circle, we can use the formula θ = (arc length) / (radius) to find the length of the arc, which is equal to the length of the wire.

Q: Can we use the formula θ = (arc length) / (radius) to find the angle subtended by the arc at the centre of the circle if we know the angle subtended by the arc at the centre of the circle and the radius of the circle?

A: Yes, we can use the formula θ = (arc length) / (radius) to find the angle subtended by the arc at the centre of the circle if we know the angle subtended by the arc at the centre of the circle and the radius of the circle. This formula is a direct application of the fact that the angle subtended by an arc at the centre of a circle is proportional to the length of the arc and inversely proportional to the radius of the circle.

Q: What is the relationship between the length of the wire and the angle subtended by the arc at the centre of the circle?

A: The length of the wire is equal to the circumference of the circle, which is proportional to the angle subtended by the arc at the centre of the circle. This means that if we know the length of the wire, we can use the formula θ = (arc length) / (radius) to find the angle subtended by the arc at the centre of the circle.

Q: Can we use the formula θ = (arc length) / (radius) to find the angle subtended by the arc at the centre of the circle if we know the length of the wire and the angle subtended by the arc at the centre of the circle?

A: Yes, we can use the formula θ = (arc length) / (radius) to find the angle subtended by the arc at the centre of the circle if we know the length of the wire and the angle subtended by the arc at the centre of the circle. This formula is a direct application of the fact that the angle subtended by an arc at the centre of a circle is proportional to the length of the arc and inversely proportional to the radius of the circle.

Conclusion

In this article, we have discussed the problem of a piece of wire bent to form an arc of a circle and the formula for finding the angle subtended by the arc at the centre of the circle. We have also answered some frequently asked questions related to this problem. The formula θ = (arc length) / (radius) is a direct application of the fact that the angle subtended by an arc at the centre of a circle is proportional to the length of the arc and inversely proportional to the radius of the circle.