Refrigerator was what is commonly used today. We do dry foods and salt cure but that is not done on a daily basis
Answer:
The rate of change of the distance between the helicopter and yourself (in ft/s) after 5 s is
ft/ sec
Explanation:
Given:
h(t) = 25 ft/sec
x(t) = 10 ft/ sec
h(5) = 25 ft/sec . 5 = 125 ft
x(5) = 10 ft/sec . 5 = 50 ft
Now we can calculate the distance between the person and the helicopter by using the Pythagorean theorem

Lets find the derivative of distance with respect to time

Substituting the values of h(t) and x(t) and simplifying we get,



=
=
ft / sec
A lodestone is a naturally magnetized piece of the mineral magnetite. They are naturally occurring magnets, which can attract iron. The property of magnetism was first discovered in antiquity through lodestones.
Answer:
1. Recollapsing universe
2. Critical universe
3. Coasting universe
Explanation:
Recollapsing universe has dark matter density greater than critical density. While critical universe has its matter density equal to the critical sensity. Coasting universe on the other hand has much smaller matter density compared to critical density.
Note that the critical density is approximately 10^-20 grams/cm3