# Chapter 27 - Worked Solutions

### to selected extension questions from the OUP text *Senior Physics -
Concepts in Context* by Walding,
Rapkins and Rossiter

**Question 17**

** **(a) Mass of components = m_{p} + m_{e }+ m_{n} x 2

= 1.007276 + 0.000549 +1.008665 x 2 = 3.025155 u

D
m = 3.016049 - 3.025155 = 9.106 x 10^{-3
}E = 931 x 9.106 x 10^{-3} = 8.4776 MeV

(b) Mass of components = m_{p} x 2 + m_{e} x 2 _{ }+ m_{n} x 1

**= **1.007276 x 2 + 0.000549 x 2 + 1.008665 = 3.024315

D
m = 3.024315 - 3.016030 = 8.285 x 10^{-3} u = 7.713 MeV

** **

**
Question 22**

(i)

(a) 16 x 1.007276 + 19 x 1.008665 + 16 x 0.000549 = 35.289835 u

D
m = 35.289835 - 34.969033 = 0.320802

(b) E = 298.66 MeV = 298.66/35 MeV/nucleon = 8.5 MeV/nucleon

(ii)

(a) 92 x 1.007276 = 92.66932

+ 143 x 1.008665 = 144.239095

+ 92 x 0.000549 = 0.050508

Total = 236.958995 u

D
m = 1.915055 u

(b) E = 1782.9 MeV = 7.58 MeV/nucleon

(iii)

(a) 48 x 1.007276 + 65 x 1.008665 + 48 x 0.000549 = 113.93825 u

D
m = 1.034417 u

(b) E = 963 MeV = 8.5 MeV/nucleon

(iv)

(a) 3 x 1.007276 + 4 x 1.008665 + 3 x 0.000549 = 7.058135 u

D
m = 0.042131 u

(b) E = 39.22 MeV = 5.6 MeV/nucleon

**Question 25**

E = 1200/(2.4 x 10^{-2}) = 50000 Vm^{-1
}m = qE/g = 3 x 1.6 x 10^{-19} x 50000/9.8 = 2.44 x 10^{-15} kg

**Question 26**

q = mg/E = 3.52 x 10^{-14} x 9.8/(9.8 x 10^{-14}) = 3.52 x 10^{-18} C

number of electrons = 3.52 x 10^{-18} C/(1.6 x 10^{-19}C) = 22

**Question 27**

D (Both particles have to be deflected; Closer particle is
deflected more).

**Question 28**

F (In the first diagram, plate X must have a negative charge,
and Y a +ve charge as the nett electrostatic force on the the positively
charge oil drop has to be upwards (to counter the downward force of
gravity). In the second diagram the electrostatic force is horizontal and to
the left (arrow G), and the gravitational force is directly down (arrow E).
The resultant force is the vector sum of these which can only be F.

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