Mastering Physics: Exercise 23.23

Mastering Physics: Exercise 23.23

Part A

Question: An electron is to be accelerated from a velocity of 3.50×10^6 m/s to a velocity of 8.50×10^6 m/s . Through what potential difference must the electron pass to accomplish this?

Answer: 

U1 − U2 = K2 − K1

K2 − K1 = 1/2 × 9.12×10^(−31) kg × ( (8.50 × 10^(6))^2 −  (3.50×10^(−6))^2 )

K2 − K1 = 2.733×10^(−17)

V = U / q

V1 − V2 = 2.733×10^(−17) / (-1.6 ×10^(−19))

V1 − V2 =  -171  V

Part B

Question: Through what potential difference must the electron pass if it is to be slowed from 8.50×10^6 m/s to a halt?

Answer: 

K2 − K1 =  1/2  × 9.12×10^(−31)  × ( 0 −  ( 8.50×10^(6))^2 )

K2 − K1 = −3.2946 ×10^(−17)

V = U / q

V1 − V2 =  −3.2946 ×10^(−17) / (−1.6×10^(×10(−

V1− V2 =  206  V