Math Problem Statement

The electric field between two parallel plates is uniform, with magnitude 650 N/C. A proton is held stationary at the positive plate, and an electron is held stationary at the negative plate. The plate separation is 4.02 cm. At the same moment, both particles are released.Calculate the distance (in cm) from the positive plate at which the two pass each other. Ignore the electrical attraction between the proton and electron.

Solution

To solve this problem, we need to calculate the point at which the proton and the electron meet after being released from rest, under the influence of a uniform electric field E=650N/CE = 650 \, \text{N/C}. The electric field will accelerate the proton and the electron in opposite directions because of their opposite charges.

Key facts:

  • The proton is positively charged, so it accelerates away from the positive plate.
  • The electron is negatively charged, so it accelerates away from the negative plate.
  • The force on a charged particle in an electric field is given by F=qEF = qE, where qq is the charge of the particle.
  • The acceleration aa is related to the force FF by Newton’s second law: F=maF = ma, where mm is the mass of the particle.

Let's break it down:

  1. Proton's acceleration: ap=qpEmpa_p = \frac{q_p E}{m_p} where qp=1.602×1019Cq_p = 1.602 \times 10^{-19} \, \text{C} (charge of proton) and mp=1.673×1027kgm_p = 1.673 \times 10^{-27} \, \text{kg}.

  2. Electron's acceleration: ae=qeEmea_e = \frac{q_e E}{m_e} where qe=1.602×1019Cq_e = 1.602 \times 10^{-19} \, \text{C} (charge of electron, same magnitude as proton but negative) and me=9.109×1031kgm_e = 9.109 \times 10^{-31} \, \text{kg}.

Next, since both particles are released simultaneously, and they start from opposite ends of the plate, we want to find the position where they meet after a certain time tt.

The positions of the proton and the electron as functions of time can be described by the kinematic equation for motion under constant acceleration: xp=12apt2x_p = \frac{1}{2} a_p t^2 xe=12aet2x_e = \frac{1}{2} a_e t^2 where xpx_p is the distance traveled by the proton from the positive plate, and xex_e is the distance traveled by the electron from the negative plate. The sum of these distances must equal the separation between the plates, which is 4.02 cm (or 0.0402 m): xp+xe=0.0402mx_p + x_e = 0.0402 \, \text{m}

Substituting for xpx_p and xex_e: 12apt2+12aet2=0.0402\frac{1}{2} a_p t^2 + \frac{1}{2} a_e t^2 = 0.0402 Simplifying: 12(ap+ae)t2=0.0402\frac{1}{2} (a_p + a_e) t^2 = 0.0402 Now, solve for t2t^2: t2=0.0402×2ap+aet^2 = \frac{0.0402 \times 2}{a_p + a_e}

Once we know tt, we can find xpx_p, the distance from the positive plate at which they meet.

Let me calculate the values for you.The proton and the electron pass each other approximately 0.22cm0.22 \, \text{cm} from the positive plate.

Would you like more details or clarifications on the steps? Here are five related questions to consider:

  1. How would the answer change if the electric field strength were doubled?
  2. What happens if the mass of the proton is significantly changed?
  3. How would this scenario differ if the electric field were non-uniform?
  4. Can we consider the proton and electron to have relativistic speeds at higher fields?
  5. How would the presence of a magnetic field affect the motion?

Tip: For problems involving uniform fields, symmetry can greatly simplify the analysis.

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Math Problem Analysis

Mathematical Concepts

Electric Fields
Kinematics
Newton's Second Law
Coulomb's Law

Formulas

Force on a charged particle: F = qE
Newton's second law: F = ma
Kinematic equation: x = (1/2)at^2

Theorems

Newton's Second Law
Coulomb's Law

Suitable Grade Level

Grades 11-12, Introductory College Physics