A man fire a bullet standing between 2 cliffs.1st echo is heard after 3 seconds and second echo is heard after 5 seconds.If velocity of sound is 330m/s, then what is the distance between 2 cliffs?

1 Answer
Tom M.
Apr 13, 2018

#1320"m"#

Explanation:

Draw a diagram.

You can only get a crude diagram on MS Paint, the most professional software out there, but that's better than nothing. You can draw a better diagram on paper, but make sure it has all the information on.

I drew this. Please be happy

I cannot emphasise the importance of a diagram. It puts all the information in one place and shows what's going on. I was struggling to figure out what to do before I drew this. If you are even slightly unsure, always always ALWAYS draw a diagram.

Back to the problem:

We want to find #d#.
#d=d_1+d_2#
So we need to find #d_1# and #d_2#

Using #s=v*t# (s is displacement, v is velocity, t is time):

#2d_1=330xx3#

For the echo to be heard, the sound needs to get to the cliff (#d_1#) and back again, hence #2d_1#.

#2d_1=990#
#d_1=495"m"#

We can do the same for the second cliff.

Using #s=v*t#

#2d_2=330xx5#

#d_2=825"m"#

All we need to do is add these up.

#d=d_1+d_2#
#d=495+825#
#d=1320"m"#

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