A joule is a unit of energy.
Answer:
c. 12,500
Explanation:
Original number of atoms = 100,000 atoms
Half- life = 10min
Unknown:
The number of atoms that will remain after 10min = ?
Solution:
The half - life is the time taken for half of a radioactive substance to decay by half.
Time taken Number of atom half life
10min 100000 _
20min 50000 1
30min 25000 2
40min 12500 3
Answer: Option (d) is the correct answer.
Explanation:
A chemical reaction in which heat energy is liberated is known as an exothermic reaction.
For example, 
In an exothermic reaction, energy of reactants is more than the energy of products.
This means that potential energy of products is less than the potential energy of reactants.
Thus, we can conclude that in the reaction 
, the potential energy of the products is less than that of the reactant.
This means acceleration a is constant.
Let
a) vo be the initial speed, at t=0
b) v be the final speed after time t
c) d distance travelled in time t
Then we have:
a) v=vo+a×t
b) v²=vo²+2×a×d (Galilei's equation)
c) d=vo×t+a×t²/2
d) average speed vm=(vo+v)/2
