Question 18 - Problems - Chapter 2¶

Problem:¶

A hunter shoots an arrow at a deer running directly away from him. When the arrow leaves the bow, the deer is at a distance of 40 m. When the arrow strikes, the deer is at a distance of 50 m. The speed of the arrow is 65 m/s.

Question:¶

a) What must have been the speed of the deer?

b) How long did the arrow take to travel to the deer?

Solution:¶

Toreach the dear, the arrow has to travel 50 m

so: Arrow Distance $s_a = 50$ m

Arrow Speed $v_a = 65$ m/s

b) Time to reach the dear: $t_a = \frac{s_a}{v_a}$

Distance that the dear has run $s_d = 50m - 40m$

The time the der has run is the same time the arrow flew $t_d = t_a$

The speed of the dear: $v_d = \frac{s_d}{t_d}$

In [1]:

sa = 50
va = 65
ta = td = sa/va
sd = 50 - 40
vd = sd / td
print(f'a) The speed of the deer is {vd:.2f} m/s.')
print(f'b) The arrow took {ta:.2f} s to reach the dear.')

a) The speed of the deer is 13.00 m/s.
b) The arrow took 0.77 s to reach the dear.

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)