When sounds at two different frequencies are combined,
two new sounds are created ... at the sum and difference
of the original frequencies.
Combining two sounds at 490 Hz and 488 Hz creates
beats at 978 Hz and 2 Hz.
The fluttering "wah wah" effect of the 2 Hz beat is much more
noticeable than the new sound at 978 Hz.
Over time, the types of technology can vary and be improved upon so that more advanced techniques become more valued. This could be the situation with mining whereby back in the 1500's in underground mines the rock was broken by fire setting ie lighting a fire below the rock face to heat up the rock and then throwing cold water on it to crack it, so that it could be dug by hand. With the advent of explosives, this all changed so that the rock could be blasted. The increase in advance rates for an underground heading have thus gone from 5-20 feet per month to up to 300meters (984 ft) per month for a 24/7 mining operation, which is a huge improvement.
A barometer is used to measure air pressure!
a) uniform velocity
b) zero or no acceleration
c) (see picture)
EXPLANATION:
(see picture)
