Answer:
A means a turning motion around a central axis tq
Answer:
4.26
Explanation:
Let the green-melon parents be Gg, then we expect the cross with the yellow-melon plant gg so as to produce 50% Gg and other 50% of gg offspring. What we observed was that 53 green and a 41 yellow. Based on the total number of 94 offspring , we expected half and a half ratios to be 47 of each color.
Observed(o) Expected(e) (o-e) 
Green-melon plant 53 47 6 36 0.766
Yellow-melon plant 41 47 -6 36 0.766
Therefore the chi-square value is 1.53 which is less than the critical value of 3.84. Therefore, the null hypothesis is accepted.
Fuel cells can make an electricity from a simple electrochemical
reaction in which oxygen and hydrogen combine to form water. There are several
different types of fuel cell but they are all based around a central design
which consists of two electrodes, a negative anode and a positive cathode.
These are separated by a solid or liquid electrolyte that carries electrically
charged particles between the two electrodes. A catalyst, such as platinum, is
often used to speed up the reactions at the electrodes. Fuel cells are
classified according to the nature of the electrolyte. Every type needs
particular materials and fuels and is suitable for any applications. The
article below uses the proton exchange membrane fuel cell to illustrate the
science and technology behind the fuel cell concept but the characteristics and
applications of the other main designs are also discussed. Proton Exchange Membrane Fuel Cells (PEMFC)
The hydrogen ions permeate across the electrolyte to the
cathode, while the electrons flow through an external circuit and provide
power. Oxygen, in the form of air, is supplied to the cathode and this combines
with the electrons and the hydrogen ions to produce water. These reactions at
the electrodes are as follows:
Anode: 2H24H+ + 4e-
Cathode: O2 + 4H+ + 4e- 2H2O
Overall: 2H2 + O22H2O + energy
PEM cells operate at a temperature of around 80°C. At this
low temperature the electrochemical reactions would normally occur very slowly
so they are catalysed by a thin layer of platinum on each electrode.
The answer is mechanical weathering
