<h3>Question:</h3>
How to find g (acceleration due to gravity)
<h3>Solution:</h3>
We know,
Acceleration due to gravity (g)

where, G = Gravitational constant

M = Mass of the earth

R = Radius of the earth

Putting these values of G, M and R in the above formula, we get

So, the value of acceleration due to gravity is

Hope it helps.
Do comment if you have any query.
The force of earth's gravitational field is always directed downwards (towards the center of the earth. When the ball is thrown up, it is going against the earth's gravitational field and so, the earth's gravitational force pulls it back down, accelerating it downwards.
Answer:
Maximum height of rocket = 2538.74 m
Explanation:
We have equation of motion s = ut + 0.5 at²
For first 5 seconds
s = 0 x 5 + 0.5 x 40 x 5² = 500 m
Now let us find out time after 5 seconds rocket move upward.
We have the equation of motion v = u + at
After 5 seconds velocity of rocket
v = 0 + 40 x 5 = 200 m/s
After 5 seconds the velocity reduces 9.8m/s per second due to gravity.
Time of flying after 5 seconds

Distance traveled in this 20.38 s
s = 200 x 20.38 - 0.5 x 9.81 x 20.38² = 2038.74 m
Maximum height of rocket = 500 +2038.74 = 2538.74 m
Answer:
The conditions necessary for hearing the echo. The distance between the sound source and the reflecting surface must not be less than 17 metres where the time period between hearing the original sound and its echo should not be less than 0.1 of a second.
The FREQUENCY of light remains unchanged once it leaves the source.