Physical changes are those change which just externally or physically change the state of the object . for example : water boils and evaporates... here the state is just changing from liquid to vapour while the composition is the same.
chemical changes are those which bring about a change in the composition of a substance. for example: burning of paper changes into ash .
Answer:

Explanation:
We know that for circular motion the centripetal acceleration
is:

where v is the speed and r is the radius.
The centripetal acceleration for the astronaut must be the gravitational acceleration due to the gravity, as there are no other force. So
.
The radius of the orbit must be the radius of the Moon, plus the 270 km above the surface




We can obtain the speed as:






And this is the orbital speed.
Explanation:
Speed is distance over time.
500 km / 2 hr = 250 km/hr
Velocity is speed and direction.
250 km/hr north
<span>Potassium carbonate (K2C03) is white salt and is often </span>found damp. It is soluble in water which makes a strong concoction. Hope this helps.
Explanation:
It is known that relation between pressure and density is as follows.
P =
where, P = pressure
= density
g = acceleration due to gravity
h = height
Putting the given values into the above formula as follows.
P =
= 
= 110495000 Pa
Now, relation between pressure and force is as follows.
P =
or, F = PA
F =
= 
Thus, we can conclude that a force of
can be experienced at such depth.