Answer:
They can't hear an echo in small room because in it the sound can't be reflected back. For an echo of a sound to be heard,the minimum distance between the source of sound and the walls of the room should be 17.2 m.
hopw it helps
Answer:
A. F=107.6nN
B. Repulsive
Explanation:
According to coulombs law, the force between two charges is express as
F=(Kq1q2) /r^2
If the charges are of similar charge the force will be repulsive and if they are dislike charges, force will be attractive.
Note the constant K has a value 9*10^9
Hence for a charge q1=7.10nC=7.10*10^-9, q2=4.42*10^-9 and the distance r=1.62m
If we substitute values we have
F=[(9×10^9) ×(7.10×10^-9) ×(4.42×10^-9)] /(1.62^2)
F=(282.4×10^-9)/2.6244
F=107.6×10^-9N
F=107.6nN
B. Since the charges are both positive, the force is repulsive
The eight planets of the Solar System arranged in order from the sun:
Mercury: 46 million km / 29 million miles (.307 AU)
Venus: 107 million km / 66 million miles (.718 AU)
Earth: 147 million km / 91 million miles (.98 AU)
Mars: 205 million km / 127 million miles (1.38 AU)
Jupiter: 741 million km /460 million miles (4.95 AU)
Saturn: 1.35 billion km / 839 million miles (9.05 AU)
Uranus: 2.75 billion km / 1.71 billion miles (18.4 AU)
Neptune: 4.45 billion km / 2.77 billion miles (29.8 AU)
Astronomers often use a term called astronomical unit (AU) to represent the distance from the Earth to the Sun.
+ Pluto (Dwarf Planet): 4.44 billion km / 2.76 billion miles (29.7 AU)
Answer:
Acceleration will be 
Explanation:
We have given initial speed of the car is 70 km/hr
We know that 1 km = 1000 m
And 1 hour = 3600 sec
So 
It is given that car stops in 12 sec
So final speed of the car v = 0 m/sec
Time t = 12 sec
From first equation of motion v = u+at
So 
( negative sign indicates that speed of the car will constantly decrease )
