Answer:
The moon's revolution around its axis and the moon's revolution around the Earth take the same time, approximately 27 days. That causes one side of the Moon to always face the Earth while the other side always faces away from the Earth. That is why it took probes to go into space to photograph the side that is never visible from Earth for people to be able to see it.
Answer:
The speed of the cart and clay after the collision is 50 cm/s .
Explanation:
Given :
Mass of lump , m = 500 g = 0.5 kg .
Velocity of lump , v = 30 cm/s .
Mass of cart , M = 1 kg .
Velocity of cart , V = 60 cm/s .
We know by conservation of momentum :

Here ,
is the speed of the cart and clay after the collision .
Putting all value in above equation .
We get :

Hence , this is the required solution .