Skip to main content
Ch 37: The Foundations of Modern Physics
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796당신이 사용하는 게 아니라요?교과서 변경
37장, 문제 44a

The oxygen nucleus ¹⁶O has a radius of 3.0 fm. With what speed must a proton be fired toward an oxygen nucleus to have a turning point 1.0 fm from the surface? Assume the nucleus remains at rest.

검증된 단계별 안내
1
Determine the total distance between the proton and the center of the oxygen nucleus at the turning point. Since the radius of the oxygen nucleus is 3.0 fm and the turning point is 1.0 fm from the surface, the total distance is \( r = 3.0 \text{ fm} + 1.0 \text{ fm} = 4.0 \text{ fm} \).
Use the concept of energy conservation. At the turning point, the proton's kinetic energy is completely converted into electric potential energy due to the repulsion between the proton and the oxygen nucleus. The total energy equation is \( K_i + U_i = K_f + U_f \), where \( K \) is kinetic energy and \( U \) is potential energy. At the turning point, \( K_f = 0 \).
Write the expression for the electric potential energy between the proton and the oxygen nucleus: \( U = \frac{k_e q_1 q_2}{r} \), where \( k_e \) is Coulomb's constant \( (8.99 \times 10^9 \text{ N·m}^2/\text{C}^2) \), \( q_1 \) is the charge of the proton \( (+e = 1.6 \times 10^{-19} \text{ C}) \), \( q_2 \) is the charge of the oxygen nucleus \( (+8e) \), and \( r \) is the distance between the charges.
Set the initial kinetic energy of the proton equal to the electric potential energy at the turning point: \( \frac{1}{2} m v^2 = \frac{k_e q_1 q_2}{r} \), where \( m \) is the mass of the proton \( (1.67 \times 10^{-27} \text{ kg}) \) and \( v \) is the initial speed of the proton. Rearrange this equation to solve for \( v \): \( v = \sqrt{\frac{2 k_e q_1 q_2}{m r}} \).
Substitute the known values into the equation for \( v \): \( k_e = 8.99 \times 10^9 \text{ N·m}^2/\text{C}^2 \), \( q_1 = 1.6 \times 10^{-19} \text{ C} \), \( q_2 = 8 \times 1.6 \times 10^{-19} \text{ C} \), \( m = 1.67 \times 10^{-27} \text{ kg} \), and \( r = 4.0 \times 10^{-15} \text{ m} \). Simplify the expression to find the speed \( v \).

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Nuclear Radius

The nuclear radius is a measure of the size of an atomic nucleus, typically on the order of femtometers (fm). For the oxygen nucleus ¹⁶O, the radius is given as 3.0 fm, which indicates the distance from the center of the nucleus to its surface. Understanding the nuclear radius is crucial for calculating distances in nuclear interactions, such as the turning point of a proton approaching the nucleus.
추천 영상:
가이드 코스
03:55
Efficiency of a Nuclear Power Plant

Turning Point in Potential Energy

The turning point in a particle's motion occurs when it can no longer continue moving toward a potential barrier, such as a nucleus, due to the repulsive forces at play. In this context, the turning point is defined as being 1.0 fm from the surface of the oxygen nucleus, which means the proton must have enough kinetic energy to reach this point before being repelled. This concept is essential for determining the required speed of the proton.
추천 영상:
가이드 코스
07:24
Potential Energy Graphs

Conservation of Energy

The principle of conservation of energy states that the total energy in a closed system remains constant. In this scenario, the kinetic energy of the incoming proton will convert into potential energy as it approaches the nucleus. By applying this principle, one can calculate the necessary speed of the proton to ensure it reaches the specified turning point before being repelled by the nucleus.
추천 영상:
가이드 코스
06:24
Conservation Of Mechanical Energy
관련 실천
교과서 질문

In one of Thomson’s experiments he placed a thin metal foil in the electron beam and measured its temperature rise. Consider a cathode-ray tube in which electrons are accelerated through a 2000 V potential difference, then strike a 10 mg copper foil. What is the electron-beam current if the foil temperature rises 6.0°C in 10 s? Assume no loss of energy by radiation or other means. The specific heat of copper is 385 J/kg K .

112
views
교과서 질문

A classical atom that has an electron orbiting at frequency ⨍ would emit electromagnetic waves of frequency ⨍ because the electron's orbit, seen edge-on, looks like an oscillating electric dipole. What is the total mechanical energy of this atom?

44
views
교과서 질문

A ²²²Rn atom (radon) in a 0.75 T magnetic field undergoes radioactive decay, emitting an alpha particle in a direction perpendicular to B\(\overrightarrow{B}\). The alpha particle begins cyclotron motion with a radius of 45 cm. With what energy, in MeV, was the alpha particle emitted?

1950
views
1
rank
교과서 질문

Physicists first attempted to understand the hydrogen atom by applying the laws of classical physics. Consider an electron of mass m and charge −e in a circular orbit of radius r around a proton of charge +e. Use Newtonian physics to show that the total energy of the atom is E =−e²/8πϵ₀𝓇

56
views
교과서 질문

The fission process n + ²³⁵U → ²³⁶U → ¹⁴⁴Ba + ⁸⁹Kr + 3n converts 0.185 u of mass into the kinetic energy of the fission products. What is the total kinetic energy in MeV?

94
views
교과서 질문

To initiate a nuclear reaction, an experimental nuclear physicist wants to shoot a proton into a 5.50-fm-diameter ¹²C nucleus. The proton must impact the nucleus with a kinetic energy of 3.00 MeV. Assume the nucleus remains at rest. Through what potential difference must the proton be accelerated from rest to acquire this speed?

38
views