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A pendulum is made from an aluminum rod with a mass attached to its free end. If the pendulum is cooled, (a) does the pendulum's period increase, decrease, or stay the same? (b) Choose the best explanation from among the following: I. The period of a pendulum depends only on its length and the acceleration of gravity. It is independent of mass and temperature. II. Cooling makes everything move more slowly, and hence the period of the pendulum increases. III. Cooling shortens the aluminum rod, which decreases the period of the pendulum.

Short Answer

Expert verified
(a) The period decreases; (b) III is correct.

Step by step solution

01

Understanding the Pendulum's Period

The period of a pendulum is given by the formula \( T = 2\pi \sqrt{\frac{L}{g}} \), where \( T \) is the period, \( L \) is the length of the pendulum, and \( g \) is the acceleration due to gravity. The period is not directly dependent on temperature or the mass of the pendulum.
02

Analyze Effects of Cooling on the Rod

Cooling the pendulum rod, which is made of aluminum, causes the rod to contract, thereby shortening its length \( L \). According to the formula from Step 1, a shorter length will lead to a decrease in the period \( T \) of the pendulum.
03

Evaluate Each Explanation Option

Let's consider each explanation: - **Option I:** It states that temperature does not affect the period, but cooling changes the rod's length, which affects the period. So this is incorrect. - **Option II:** Suggests that cooling makes the whole system slower, which isn't true for the mechanical operation of a pendulum, especially in a physics context. - **Option III:** States that cooling shortens the rod and decreases the period, which matches the derived conclusion from Steps 1 and 2.

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Key Concepts

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

Temperature Effects on Pendulum
When discussing pendulums, one might wonder how changes in temperature might impact their behavior. A pendulum’s period is generally determined by its length and the gravitational force acting on it. However, temperature can indirectly influence the period by affecting the physical properties of the materials used. When a pendulum like the one in the exercise is cooled, particularly if it is made of a material such as aluminum, the metal contracts. This contraction alters the length of the pendulum's rod.

When the temperature drops, the physical contraction of the pendulum's rod results in a shorter length. According to the relationship between pendulum length and period, a shorter length leads to a shorter period. Most importantly, this means that while temperature doesn't directly impact the period, it does play a significant role through the thermal properties of the rod material.
  • Cooling causes materials to contract.
  • Contraction of the rod reduces its length.
  • Resulting decrease in pendulum period due to shorter length.
Pendulum Length and Period
Understanding the connection between the length of a pendulum and its period is crucial in many physics applications. The period of a pendulum, which is the time it takes for the pendulum to complete one full swing, is given by the formula: \[ T = 2\pi \sqrt{\frac{L}{g}} \] Here, \( T \) is the period, \( L \) is the length of the pendulum's rod, and \( g \) is the acceleration due to gravity.

The formula tells us that the pendulum's period is directly related to the square root of its length. Thus, any changes in the length of the pendulum will have a proportionate effect on its period. For example, if the length increases, the period increases, as the pendulum takes longer to complete a swing. Likewise, a reduction in length results in a shorter period. Importantly, this formula highlights that gravity and length are the main determinants of the pendulum's timing, with other factors such as temperature affecting the period only indirectly through changes in length.
  • Period relies on the length of the pendulum.
  • Increase in length leads to increase in period.
  • Reduction in length leads to shorter period.
Thermal Contraction in Materials
Thermal contraction refers to the decrease in physical size or dimensions of a material when its temperature drops. This concept is essential when analyzing structures or systems affected by temperature changes, such as in the case of a pendulum made from aluminum. Different materials have varying reactions to temperature changes, often measured as the coefficient of thermal expansion.

Aluminum, for instance, has a specific coefficient of thermal expansion, which describes how much it will contract per degree decrease in temperature. The impact this contraction has on systems, like the pendulum, is crucial to consider. A decrease in temperature causes the rod to shrink, reducing its length and consequently altering the pendulum's period.
  • Thermal contraction is the physical reduction in size due to cooling.
  • Coefficient of thermal expansion quantifies material’s response to temperature change.
  • Important in accurately predicting changes in systems relying on precise measurements, like pendulums.

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Most popular questions from this chapter

Two metal rods-one lead, the other copper-are connected in series, as shown in Figure \(16-18\). These are the same two rods that were connected in parallel in Example \(16-7 .\) Note that each rod is \(0.525 \mathrm{m}\) in length and has a square cross section \(1.50 \mathrm{cm}\) on a side. The temperature at the lead end of the rods is \(2.00^{\circ} \mathrm{C} ;\) the temperature at the copper end is \(106^{\circ} \mathrm{C} .\) (a) The average temperature of the two ends is \(54.0^{\circ} \mathrm{C}\). Is the temperature in the middle, at the lead- copper interface, greater than, less than, or equal to \(54.0^{\circ} \mathrm{C}\) ? Explain. (b) Given that the heat flow through each of these rods in \(1.00 \mathrm{s}\) is \(1.41 \mathrm{J}\), find the temperature at the lead- copper interface.

Two objects are made of the same material but have different temperatures. Object 1 has a mass \(m\) and object 2 has a mass \(2 m\). If the objects are brought into thermal contact, (a) is the temperature change of object 1 greater than, less than, or equal to the temperature change of object \(2 ?\) (b) Choose the best explanation from among the following: I. The larger object gives up more heat, and therefore its temperature change is greatest. II. The heat given up by one object is taken up by the other object. since the objects have the same heat capacity, the temperature changes are the same. III. One object loses heat of magnitude \(Q\), the other gains heat of magnitude Q. With the same magnitude of heat involved, the smaller object has the greater temperature change.

A pendulum consists of a large weight suspended by a steel wire that is \(0.9500 \mathrm{m}\) long. (a) If the temperature increases, does the period of the pendulum increase, decrease, or stay the same? Explain. (b) Calculate the change in length of the pendulum if the temperature increase is \(150.0 \mathrm{C}^{\circ}\) (c) Calculate the period of the pendulum before and after the temperature increase. (Assume that the coefficient of linear expansion for the wire is \(12.00 \times 10^{-6} \mathrm{K}^{-1}\) and that \(g=9.810 \mathrm{m} / \mathrm{s}^{2}\) at the location of the pendulum.)

Greatest Change in Temperature A world record for the greatest change in temperature was set in Spearfish, SD, on January 22,1943 . At 7: 30 a.M. the temperature was \(-4.0^{\circ} \mathrm{F}\); two minutes later the temperature was \(45^{\circ} \mathrm{F}\). Find the average rate of temperature change during those two minutes in kelvins per second.

Normal body temperature for humans is \(98.6^{\circ} \mathrm{F}\). What is the corresponding temperature in (a) degrees Celsius and (b) kelvins?

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