(8%) Problem 11: An electron has an initial velocity of 4.8 × 106 m/s in a unifo

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(8%) Problem 11: An electron has an initial velocity of 4.8 × 106 m/s in a uniform 1.85 × 105 N/C electric field. The field accelerates the electron in the direction opposite to its initial velocity.

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Note: answers without explenations will not get credit

25% Part (a) What is the direction of the electric field? The field is in the opposite direction of the electron's initial velocity. The field is in another direction not listed here. The field is in the direction of the electron's initial velocity. The field is in the direction to the right of the electron's initial velocity.

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Deductions 0% Potential 100%

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Attempts remaining: 3 (33% per attempt) detailed view Hints: 4% deduction per hint. Hints remaining: 3 Feedback: 5% deduction per feedback. 25% Part (b) How far does the electron travel before coming to rest in m?
25% Part (c) How long does it take the electron to come to rest in s?
25% Part (d) What is the magnitude of the electron's velocity (in m/s) when it returns to its starting point in the opposite direction of its initial velocity?

Explanation / Answer

here ,

initial speed , u = 4.8 *10^6 m/s

elctric field , E = 1.85 *10^5 N/C

a) as the electron is accelerating oposite to velocity

electron is negative charged

force is opisite to the electric field

The field is in the direction of the electron's initial velocity.

b)

let the acceleration is a

using second equation of motion

a * m = e * E

a * 9.11 *10^-31 = 1.602 *10^-19 * 1.85 *10^5

a = 3.25 * 10^16 m/s^2

let the distance is d

Using third equation of motion

v^2 - u^2 = 2 * a * d

(4.8*10^6)^2 = 2 * 3.25 * 10^16 * d

d = 3.54 *10^-4 m

electron will travel 3.54 *10^-4 m before stopping

part c)

let time taken is t

t = v/a

t = 4.8 *10^6/(3.25 * 10^16)

t = 1.48 *10^-10 s

the time taken is 1.48 *10^-10 s

part d)

as electric field is conservative field

the velocity of electron will be same at the same initial position

speed of electron = 4.8 *10^6 m/s

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