Because they are. it’s just how life works
Energy is measured by joule(j)

Explanation:
At the top of the tree, the velocity of the pebble is purely horizontal so we can calculate it as


Answer: a) 3.85 days
b) 10.54 days
Explanation:-
Expression for rate law for first order kinetics is given by:

where,
k = rate constant = ?
t = time taken for decomposition = 3 days
a = let initial amount of the reactant = 100 g
a - x = amount left after decay process = 
First we have to calculate the rate constant, we use the formula :
Now put all the given values in above equation, we get


a) Half-life of radon-222:


Thus half-life of radon-222 is 3.85 days.
b) Time taken for the sample to decay to 15% of its original amount:
where,
k = rate constant = 
t = time taken for decomposition = ?
a = let initial amount of the reactant = 100 g
a - x = amount left after decay process = 


Thus it will take 10.54 days for the sample to decay to 15% of its original amount.
For the majority of instruments f = n f0 where f is the resonating frequency, n is any whole number and f0 is the fundamental.
<span>This applies to trumpets, violins, flutes and a broad range. </span>
<span>In such a </span>case<span> the first harmonic would be at n=1 and the second harmonic would be at n=2 </span>
<span>which gives a frequency of 84 Hz</span>