Why machines are sometimes jammed in winter?

Why is there summer in December and winter in June in the southern hemisphere?

Why do we wear woolen clothes in winter?

Pendulum clocks may run slow in summer and fast in winter .Why?

Why a fan continues to rotate for sometime even after it is switched off ?

Why does the body of a bus begins to rattle sometimes when the bus picks up the speed?

A factory owner wants to purchase two types of machines A and B, for his factory. The machine A requries an area of 1000m^2 and 12 skilled men for running it and its daily output is 50 units. Whereas the machine B are requries 1200m^2 area and 8 skilled man, and its daily output is 40 units. if an area of 7600m^2 and 72 skilled men be availabe to operate the machines,how many machines of each type should be brought to maximize the daily output.

Justify the statement, "sometimes a wine glass is broken by the powerful voice of celebrated singer."