A. Equal and opposite forces
Explanation:
History law states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exert an equal and opposite force on object A
Heat from burning fuel warms the walls of the firebox section of the furnace in
A. a hot-water heating system.
B. a hot-air heating system.
C. a compressor compartment.
D. an evaporation system.
Answer:
The Gravitational Force is reduced 4 times
Explanation:
The equation of Gravitational force follows:
F = (G*m1*m2)/r^2
Assume that G*m1*m2 = 1 and r = 1:
F = 1/1^2 = 1 N
Multiply the radius by 2
F = 1/2^2 = 1/4 N
So doubling the distance reduces the force 4 times.
Wearing rubber or stay away from water or/ and a conductor
Answer:
b) 472HZ, 408HZ
Explanation:
To find the frequencies perceived when the bus approaches and the train departs, you use the Doppler's effect formula for both cases:

fo: frequency of the source = 440Hz
vs: speed of sound = 343m/s
vo: speed of the observer = 0m/s (at rest)
v: sped of the train
f: frequency perceived when the train leaves us.
f': frequency when the train is getTing closer.
Thus, by doing f and f' the subjects of the formulas and replacing the values of v, vo, vs and fo you obtain:

hence, the frequencies for before and after tha train has past are
b) 472HZ, 408HZ