The two different isotopes have weights :
w1 = 78.918 amu
w2 = 80.916 amu
average weight w3 = 79.903 amu
The mixing of two components can be modeled as
let the fraction of w1 be 'x'
hence 
now this is a linear equation in 'x'. Substituting the values we get
x = 0.507
hence the percentage of Br79 = 50.7% and the percentage of BR81 = 49.3%
I would think force. Because friction has to have force to work ^-^
Answer:
No,
Explanation:
An electromagnetic wave is made of vibrating electric and magnetic fields that continually induce each other; matter is not needed for this to occur.
Answer:
None, egg cells don't have chromosomes. No, sex cells do have chromosomes. Meiosis reduces chromosome number so that sex cells (eggs and sperm) have a half set of chromosomes–one homolog of each pair. This is the haploid number.
Answer:
Peer Review
Explanation:
When scientist check other scientists the process is dubbed "peer review".