Answer: The rising and setting of the Sun.
The appearance and disappearance of the Moon.
Changes in season.
Appearance and disappearance of the Stars.
Explanation: The rising and setting of the Sun helps can be used as a standard to determine time since the rissing and setting of the Sun occurs at similar time and interval in a given geographical ocation.
The appearance and disappearance of the Moon which occurs during the night and early hours of the morning is similar in a given geographical locationation so it can be used as a standard for Time.
Change in season is another natural phenomenon which occurs at similar times in a given geographical location like Winter/summer, rainy/dry etc can be used as standards for time.
The appearance and disappearance of the Stars can also b used as standards for time in a given geographical location.
Answer: 17.59 Hz and 4.87 m
Explanation:
The fundamental frequency of the sound from an open-open pipe is given as
f= 
where v= 343 m/s
L= 32 feet= 
= 9.75 m
So,
f= 
= 17.59 Hz
The length of open-closed tube is related to frequency by formula
f= 
or L=
L= 
L= 4.87 m
Mechanical energy is the sum of E potensial and E kinetical
Answer:
Its state is in uniformly accelerated motion
Explanation:
When an object is acted upon the force of gravity only, we said that the object is in free fall.
According to Newton's second law of motion:
where F is the net force on an object, m is its mass, a its acceleration, when the net force on an object (F) is non-zero, than the object accelerates (because a is non-zero), so the object is in accelerated motion.
In case of free fall, the rate of acceleration of the object is equal to 
, the acceleration due to gravity, and it is constant. So, the object is moving by uniformly accelerated motion.
They are easy to use and more reliable
