A charge falls from infinity to within r of another charge, find velocity.

Click For Summary
SUMMARY

The velocity of an electron falling from infinity to a distance of r=10^-8m from a charge q1=4.8x10^-19C is calculated using the principles of potential and kinetic energy. The potential energy change (U) is determined using the formula U=k(q1)(q2)/r, resulting in U=6.912x10^-21J. By equating potential energy to kinetic energy (Ek=½mv²), the velocity is derived as v=(2U/m)^(0.5), yielding a final velocity of 1.23x10^5 m/s. Attention to the power of ten is crucial in ensuring accurate calculations.

PREREQUISITES
  • Understanding of Coulomb's law and electric potential.
  • Familiarity with kinetic energy equations.
  • Knowledge of constants such as Coulomb's constant (k) and electron properties.
  • Basic algebra for manipulating equations and solving for velocity.
NEXT STEPS
  • Review the derivation of Coulomb's law and its applications in electrostatics.
  • Study the concepts of potential energy and kinetic energy in the context of charged particles.
  • Learn about the implications of significant figures and powers of ten in scientific calculations.
  • Explore advanced topics in electrostatics, such as electric fields and forces between charges.
USEFUL FOR

Students in physics, particularly those studying electromagnetism, as well as educators and anyone interested in the dynamics of charged particles in electric fields.

User1247
Messages
16
Reaction score
0

Homework Statement


Velocity of an electron that falls to r from infinity?
An electron falls from infinity to r=10^-8m from a charge q1=4.8x10^-19C. What is the velocity of the electron?






Homework Equations


U=q1V
V=kq2/r

The Attempt at a Solution


Potential energy change U. coulomb's constant k=9x10^-9, electron charge q2=1.602x10^-19C, electron mass m=9.11x10^-31kg, kinetic energy Ek=½mv²

U=k(q1)(q2)/r=6.912x10^-21J
set U=Ek => v=(2U/m)^0.5=1.23x10^5m/s

Anyone see where I went wrong? Thanks.
 
Physics news on Phys.org
User1247 said:
U=k(q1)(q2)/r=6.912x10^-21J
Redo this, paying attention to the power of ten.
 

Similar threads

  • · Replies 7 ·
Replies
7
Views
1K
  • · Replies 3 ·
Replies
3
Views
16K
Replies
13
Views
1K
  • · Replies 39 ·
2
Replies
39
Views
4K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
1
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 3 ·
Replies
3
Views
11K
  • · Replies 1 ·
Replies
1
Views
7K