Sound level at distance of 15 m is given as 20 dB
so intensity at this distance is given as
now if we move closer to some some distance the sound level is now 50 dB
now the intensity is given as
now we know that
so now the distance from friend must be 47 cm
Brass requires more energy than silver
Aluminum requires more energy than copper
Aluminum requires more energy than brass
Explanation:
The specific heat capacity of a substance indicates the amount of heat energy required to raise 1 kg of that substance by 1 degree in temperature.
Mathematically:
where
Q is the heat supplied to the substance
m is the mass of the substance
is the change in temperature
Therefore, the higher the specific heat capacity of a substance, the more energy is needed to increase its temperature.
Here we can compare the specific heat capacity of the materials mentioned:
Silver:
Brass:
Platinum:
Aluminium:
Copper:
Therefore, the correct statements are:
Brass requires more energy than silver
Aluminum requires more energy than copper
Aluminum requires more energy than brass
Learn more about specific heat:
#LearnwithBrainly
Answer:
F = 352 N
Explanation:
we know that:
F*t = ΔP
so:
F*t = M-M
where F is the force excerted by the wall, t is the time, M the mass of the ball, the final velocity of the ball and
the initial velocity.
Replacing values, we get:
F(0.05s) = (0.8 kg)(11m/s)-(0.8 kg)(-11m/s)
solving for F:
F = 352 N