T = half life period of decay for atoms of element A = 20,000 years
N₀ = initial number of atoms of element A = 10,000 atoms
N = final number of atoms after time "t" = 2500 atoms
t = time of decay = ?
λ = decay constant = ?
decay constant is given as
λ = 0.693/T
λ = 0.693/20,000
λ = 0.00003465 years⁻¹
atoms after decay for time "t" is given as
N = N₀ 
inserting the values
2500 = (10000) 
t = 40,000 years
so correct choice is
B) 40,000 years
Could be that the speed of sound is 330m/s
B) Energy from the sun is the answer, I am sure;
The water cycle is driven primarily by the energy from the sun<span>
. This </span>
solar energy<span>
drives the cycle by evaporating water from the oceans, lakes, rivers, and even the soil. Other water moves from plants to the atmosphere through the process of transpiration.</span>
Answer:
the answer is C
Explanation:
gravity forces down not up or sideways.
1. The chemical reaction produced by Carlo's fire is exergonic because energy is "going out". As the reaction proceeds, entropy increases as the energy stored in the dry wood and leaves are used up as fuel to create the fire which produces low quality light and warmth.
2. This reaction is a classic example of an exothermic reaction. Exothermic reactions are characterized with the presence of heat and light in the products. Combustion reactions are always exothermic in nature.
3. Catalyst are substances that are used to speed up reactions by lowering the activation requirement. Catalysts aren't consumed in the reaction and can still be chemically retrieved afterwards. In this situation, the leaves cannot be retrieved after the reaction ends. The leaves speed up the heating of the wood but it does not behave as a catalyst.
