Explain why :

1) It is easier to pull a lawn roller ? 

2) The maximum height of the mountain on the earth is not more than 10 K.M.?

 Hi Ankur

 Have a look at the given figure:

In case of pushing a roller, if you resolve the applied force into horizontal and vertical directions, effective weight of the roller increases.

On the other hand in case of pulling force, if you resolve the applied force into horizontal and vertical directions, effective weight of the roller decreases.

Thus, we conclude that it is easier to pull a lawn roller as compared to push it.

There is a limit at which a mountain remains stable.

On earth one of the biggest limiting factors is erosion. Higher the mountain the more energy that can be released by rolling a rock down it, so higher will be the rate of erosion. So mountain isn't being built as fast as it is being eroded, hence it won't be growing.

The other effect is that the plates, on which mountains are built, are floating on the mantle. To build a mountain higher you have to make the plate thicker (as compared to that of natural one) so that it floats.

I hope it helps you

Cheers!!