Chapter-2 Q008 - Physics For Engineers And Scientists - Solutions

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Question 8 - Problems - Chapter 2

Problem:

In 1971, Francis Chichester, in the yacht Gypsy Moth V, attempted to sail the 4000 nautical miles (nmi) from Portuguese Guinea to Nicaragua in no more than 20 days.

Question:

a) What minimumaverage speed (in nmi/h) does it require to mkz the whole trip?

b) After sailing 13 days, he had still 1720 nmi to go. What minimum average speed did he require to reach his goal in the remaining 7 days?

c) Knowing that his yacht could at best achieve a maximum speed of 10 nmo/h, what could he conclude at this point?

Solution:

Total Distance $s = 4000$ nmi

Time = $t = 20$ days$

Average speed $v = \frac{s}{t}$

In [1]:
Distance_tot = 4000 # in nmi
Time_tot = 20 * 24 # in hours
Avg_Speed_tot = Distance_tot / Time_tot
print(f'a) The needed average speed for the total race is {Avg_Speed_tot:.1f} nmi/h.')
Distance_rest = 1720
Time_rest = 7 * 24
Avg_Speed_rest = Distance_rest / Time_rest
print(f'b) The needed average speed to sail the rest-distance within the required time is {Avg_Speed_rest:.1f} nmi/h')
if Avg_Speed_rest <= 10:
    print('c) Yes he can make it within the required time.')
else:
    print('c) No he cannot make it within the required time')
a) The needed average speed for the total race is 8.3 nmi/h.
b) The needed average speed to sail the rest-distance within the required time is 10.2 nmi/h
c) No he cannot make it within the required time

سُوۡرَةُ حٰمٓ السجدة / فُصّلَت
ثُمَّ اسْتَوَىٰ إِلَى السَّمَاءِ وَهِيَ دُخَانٌ فَقَالَ لَهَا وَلِلْأَرْضِ ائْتِيَا طَوْعًا أَوْ كَرْهًا قَالَتَا أَتَيْنَا طَائِعِينَ ﴿١١
فَقَضَاهُنَّ سَبْعَ سَمَاوَاتٍ فِي يَوْمَيْنِ وَأَوْحَىٰ فِي كُلِّ سَمَاءٍ أَمْرَهَا ۚ وَزَيَّنَّا السَّمَاءَ الدُّنْيَا بِمَصَابِيحَ وَحِفْظًا ۚ ذَٰلِكَ تَقْدِيرُ الْعَزِيزِ الْعَلِيمِ ﴿١٢


Surah Fussilat: Thereafter turned He to the heaven and it was as smoke, and said Unto it and Unto the earth: come ye twain, willingly or loth. They said: we come willingly. (11) Then He decreed them as seven heavens in two days, and revealed Unto each heaven the command thereof; and We bedecked the nether heaven with lamps and placed therein a guard. That is the ordinance of the Mighty, the Knower. (12)

De hemelen en aarde (waren) een samenhangende massa. Wij hebben ze toen van elkaar gescheiden… Wij hebben de hemel tot een beschermend dak gemaakt … en de dag en de nacht, de zon en de maan geschapen. (Koran 41 11:12)


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