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Ch 10: Interactions and Potential Energy
Chapter 10, Problem 10

FIGURE 10.23 showed the potential-energy curve for the O2 molecule. Consider a molecule with the energy E1 shown in the figure. a. What is the maximum speed of an oxygen atom as it oscillates back and forth? Don't forget that the kinetic energy is the total kinetic energy of the system. The mass of an oxygen atom is 16 u, where 1 u=1 atomic mass unit =1.66×10(to the poer of)−27 kg .

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1
Identify the total energy (E1) of the system from the potential-energy curve. This total energy is the sum of potential energy and kinetic energy at any point in the oscillation.
Determine the minimum potential energy (U_min) from the potential-energy curve. The maximum kinetic energy (K_max) occurs when the potential energy is at its minimum, and can be calculated using the equation K_max = E1 - U_min.
Recall that the total kinetic energy of the system includes the kinetic energy of both oxygen atoms in the molecule. Since the molecule consists of two identical atoms, each atom will have half of the total kinetic energy. Therefore, the kinetic energy of one oxygen atom is K_atom = K_max / 2.
Use the kinetic energy formula for one oxygen atom, K_atom = 0.5 * m * v^2, where m is the mass of an oxygen atom and v is the speed of the atom. Solve for v (the speed of the oxygen atom) by rearranging the formula to v = sqrt(2 * K_atom / m).
Substitute the values for K_atom and m (mass of an oxygen atom = 16 u = 16 * 1.66×10^(-27) kg) into the equation to find the maximum speed of the oxygen atom.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Potential Energy Curve

A potential energy curve represents the potential energy of a system as a function of the position of its components. In the context of molecular oscillations, it illustrates how the energy of a molecule changes as it moves between different positions, indicating stable and unstable configurations. The shape of the curve helps determine the energy states and the behavior of the molecule, including oscillation frequencies and maximum speeds.
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Kinetic Energy

Kinetic energy is the energy possessed by an object due to its motion, calculated using the formula KE = 1/2 mv², where m is mass and v is velocity. In the context of oscillating molecules, the total kinetic energy of the system is crucial for determining the maximum speed of the atoms. As the potential energy decreases, the kinetic energy increases, allowing for the calculation of the maximum speed at which the atoms can oscillate.
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Mass and Atomic Units

Mass in physics is a measure of the amount of matter in an object, typically expressed in kilograms or atomic mass units (u). In this question, the mass of an oxygen atom is given as 16 u, which can be converted to kilograms using the conversion factor 1 u = 1.66 × 10⁻²⁷ kg. Understanding the mass of the atom is essential for calculating its kinetic energy and, consequently, its maximum speed during oscillation.
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