A charge q moves from point A to point B. The potential energy of the charge at point A is 5.3 × 10^-10 joules and at point is B is 3.1 × 10^-10 joules. If the kinetic energy of the charge at point A is zero, what is the kinetic energy at point B?

A. 8.4 × 10^-10 joules
B. 5.3 × 10^-10 joules
C. 3.1 × 10^-10 joules
D. 2.2 × 10^-10 joules
E. 1.5 × 10^-10 joules

Question

A charge q moves from point A to point B. The potential energy of the charge at point A is 5.3 × 10^-10 joules and at point is B is 3.1 × 10^-10 joules. If the kinetic energy of the charge at point A is zero, what is the kinetic energy at point B?

A. 8.4 × 10^-10 joules
B. 5.3 × 10^-10 joules 
C. 3.1 × 10^-10 joules 
D. 2.2 × 10^-10 joules
E. 1.5 × 10^-10 joules

anonymous · Answer

Okay so, TOTAL energy. Must always remain the same. However, it can be transferred to different forms such as (Potential, Kinetic). and in this case we are only worried about those two types. So what we have here mathematically is that...$$E_{a}=E_{b}$$
(Now in this case the total energy is the sum of the potential and kinetic)
$$U_{a} + K_{a}= U_{b} + K_{b}$$
Can you try it from here?

anonymous · Answer

im still confused lol.. :C

anonymous · Answer

just tell me what #'s to plug in & Ill try to solve it?

anonymous · Answer

I want you to understand this! So U(a) is the potential energy at point A 
U(b) is the potential at point B
K(a) is the kinetic at A, which we know is zero, so that term drops out
K{b} is the kinetic at B, which is what you want to know!

anonymous · Answer

I get the numbers now , I just dont know how to solve it ?

anonymous · Answer

Do i divide 5.3*10^-10 by 3.1*10^10?

anonymous · Answer

I got 1.7 something .. Do I just go with E?