• Support PF! Buy your school textbooks, materials and every day products Here!

Double the speed

  • Thread starter channel1
  • Start date
  • #1
73
0

Homework Statement


A proton is accelerated from rest through a potential difference of 500MV. Classical mechanics indicates that quadrupling the potential difference would double the speed. Were a classical analysis valid, what speed would result from a 2000MV potential difference?


Homework Equations



4V->2v

The Attempt at a Solution


We were first asked to find the original speed of the proton going through 500MV which is 0.76c Since 2000MV = 4*500MV and 4V means v is doubled, why can't I just double 0.76c to get the new speed for the proton accelerated through the 2000MV?
 

Answers and Replies

  • #2
SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
11,224
951

Homework Statement


A proton is accelerated from rest through a potential difference of 500MV. Classical mechanics indicates that quadrupling the potential difference would double the speed. Were a classical analysis valid, what speed would result from a 2000MV potential difference?

Homework Equations



4V->2v

The Attempt at a Solution


We were first asked to find the original speed of the proton going through 500MV which is 0.76c Since 2000MV = 4*500MV and 4V means v is doubled, why can't I just double 0.76c to get the new speed for the proton accelerated through the 2000MV?
I believe that you are asked to do precisely that.
 
  • #3
73
0
Yet the answer is 2.07c :/
 
  • #4
73
0
the book solves it by 4*(the original KE, 8*10^-11 J) = .5 * m * v^2 then solving for v.......but I really just don't see why I can't logically just straight-up double the velocity...
 

Related Threads for: Double the speed

Replies
3
Views
4K
Replies
1
Views
496
Replies
3
Views
2K
Replies
1
Views
3K
Replies
9
Views
11K
  • Last Post
Replies
6
Views
186
Top