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
Answer:
d)
Explanation:
Electrons are lost or gained when the ballon is rubbed with a PVC. As the rubber ballon lost electrons, it will have more protons, hence the positive charge. (More protons than electrons in the ballon).
Answer:
d = V/E
Explanation:
From the definition, we can say that the electric field strength between the plates of a parallel plate capacitor is
E = v/d
where
E = electric field strength
V = potential difference
d = distance between the plates
On rearranging the equation and making d subject of the formula, we have
d = V/E
From the question, we're given that
V = 112 V
E = 1.12 kV/cm converting to V/m, we have 110000 V/cm
d = 112 / 110000
d = 0.00102 m
d = 1.02*10^-3 m
10.67m/s²
32N
Explanation:
Given parameters:
Mass of the body = 3kg
velocity of the mass = 4m/s
radius of circle = 0.75m
Unknown:
centripetal acceleration = ?
centripetal force = ?
Solution:
The centripetal force is the force that keeps a radial body in its circular motion. It is directed inward:
Centripetal acceleration = 
v is the velocity of the body
r is the radius of the circle
putting in the parameters:
Centripetal acceleration = 
Centripetal acceleration = 10.67m/s²
Centripetal force = m
m is the mass
Centripetal force = mass x centripetal acceleration
= 3 x 10.67
= 32N
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