Solution:

Felix

Explanation:
Iron = Fe (chemical symbol)
59 = LIX (Roman numerals)

Solution:

a) Immediately

Explanation:
"Temperature difference" is the driving force for the heat transfer.
Since the coffee is initially very hot and hence it will be cool down at a very fast rate.
If we add cream immediately : The temperature will initially go down for sure but then will cool down at the slower rate as coffees mixed with cream is cooler than coffee alone and therefore heat cool down rate is less. Also, the cream will increase the mass of the content in the cup and hence larger mass will take more time to cool down.
Hence cream should be added immediately

Solution:

As shown in the picture below, you should tilt the barrel so the liquid will touch the upper end of the barrel. So if the bottom part of the barrel is visible then it's not half full.

Solution:

It's Ice.

Solution:

When he is rowing the boat in the river, the boat is floating with watermelons in it and, therefore, all the watermelons have already displaced the water equal to their volume. Hence, there won't be any change in the water level, whether the farmer eats it or throws them away.

Solution:

Both will rotate at Same speed.

Explanation:
Gears of the same size will always rotate at constant speeds despite any smaller or larger gears in between them.

Solution:

The equator.

I stand up straight wrt ground, but is sideways wrt Earth axis.

Solution:

32 Degrees Fahrenheit at which Water Freezes.

Solution:

The torque needed to hold up the longer piece is responsible for the fact that the shorter piece will weigh more. This is the reason why a heavier kid sits closer in on a see-saw against a lighter kid.

Solution:

Yes there is a way considering if you can find a magnifying glass. Using the bright sunrays, you can then burn away the string allowing the ring to fall down on the bottom of the bottle.