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
B is the correct answer because an object moving ten north m/s will turn into 15m/s which as you can tell is accelerating.
Answer:
the ability to disolve in water is solubility
Answer:
20600N
Explanation:
Given parameters:
Mass of the roller coaster = 515kg
radius = 10m
Speed = 20m/s
Unknown:
Force of the track pushing up on the vehicle = ?
Solution:
The force pulling the roller coaster along the track is the centripetal force.
To find the centripetal force, use the expression below;
F =
where;
m is the mass
v is the speed
r is the radius
Now insert the parameters and solve;
F =
= 20600N