Question

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?

Answer 1

`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 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"`