Chapter-2 Q021 - Physics For Engineers And Scientists - Solutions

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Amateur Radio and Astronomy website. JO10UX

Question 21 - Problems - Chapter 2

Problem:

The distance for a marathon is 26 mi 385 yd. In 1984, Joan Benoit set an Olympic record with a time of 2 h 24 min 52 s.

Question:

What was her average speed in m/s?

Solution:

Distance $s = 26$ mi $385$ yd

Time $t = 2$ h $24$ min $52$ s

By mean of introduction, we will use the unit conversion modules Pint

In [1]:
# See if the library module "pint" is installed, if not download and install it 
# pint is not installed by default in anaconda
#
# if you want to install in anaconda use this command in the anaconda console:
#     conda install -c conda-forge pint
#
# if you do not use anaconda this script will install pint by the operating system
#
try:  
    import pint
except:
    import os
    os.system('pip install pint')    
    import pint

from datetime import timedelta
u = pint.UnitRegistry()

Time = timedelta(hours=2, minutes=24, seconds=52)
Distance = 26 * u.mile + 385 * u.yd # in m
Speed = Distance.to(u.m) / (Time.total_seconds() * u.s)
print(f'His average speed was {Speed:.1f} . (or {Speed.to(u.km / u.hour):.1f}).')
His average speed was 4.9 meter / second . (or 17.5 kilometer / hour).

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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