A tree getting struck by lightning, it is an example of a physical change.
It is so because when a tree getting struck by lightning, it encountered a strong force of power but no new substance is formed here. So it is a physical change, if it is a chemical change then a new substance must formed here. So when a tree getting struck by lightning, it is an example of a physical change.
Answer:
visbility if that is an answer
Explanation:
The number 7 is the coefficient
W=m₁/m₀=2^(-t/T)
t=4.6·10⁹ years
T=5·10¹⁰ years
w=2^(-4.6·10⁹/5·10¹⁰)
w=0.9382
w=93.82%
66.8g to mg is 66800 hope this helps