Answer: D.) 39,200 J
Via the equation of potential energy PE = mgh where m is mass, g is the average gravity on earth and h is the height. In this case m = 400 kg, g = 9.8, h = 10 m thus:

P.E.= 39,200 Joules
Answer:
Instantaneous speed means speed at any instant
that means Speed is changing with time
You know speed is distance/time
So that means distance is also changing with time
So we take infinitesimal small distance per infinitesimal small time As we assume speed is constant in infinitesimal small time dt
So, we take speed = ds/dt
ds = infinitesimal small distance
dt = infinitesimal small time
As its ratio is equal to speed at any instant
Note : We are taking infinitesimal small distance
But :) we are taking infinitesimal small time also
As you know if denominator is small fraction is large So fraction always give large value
So it's not O ( this makes confuse to most of students)
So, thanks
Good question
Keep thinking like this :)
Newton's first law of motion best illustrates the principle of inertia<span />

Explanation:
The acceleration due to gravity g is defined as

and solving for R, we find that

We need the mass M of the planet first and we can do that by noting that the centripetal acceleration
experienced by the satellite is equal to the gravitational force
or

The orbital velocity <em>v</em> is the velocity of the satellite around the planet defined as

where <em>r</em><em> </em>is the radius of the satellite's orbit in meters and <em>T</em> is the period or the time it takes for the satellite to circle the planet in seconds. We can then rewrite Eqn(2) as

Solving for <em>M</em>, we get

Putting this expression back into Eqn(1), we get



