Question

a.why is it necessary to grease machines regularly?
b.why are there grooves in tyres and wheels of auto mobiles?
c. why is it difficult to walk on a muddy surface?

Answer 1

Here are the answers for these questions:

a. It is necessary to grease machine regularly to reduce friction in moving    parts and ensure smooth action.

b. There are grooves in tires of automobile to provide extra traction to the surface, else you would slip off..

c. It is difficult to walk on muddy terrain because mud is slimy when it is with fluid. People's feet sinking the mud making traction difficult.