C ,A ,B ,D
I think I’m to sure
C.
The particles move perpendicular to the direction of the wave.
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
The object<span> is moving with a decreasing acceleration. The </span>object<span> is moving with </span>a constant<span> velocity.</span>
Place the boxes 10cm apart, if they are closer that concentrates the mass of the boxes more