00:01
Hello and welcome to this video solution of numerate.
00:03
Here it's given that rain drops of mass m are falling vertically with a speed v.
00:10
So with speed v it's falling down and with a flux density of n drops per unit area per unit time.
00:18
So n drops per area time.
00:35
An athlete runs through this rain on a horizontal track with a speed w.
00:43
Her cross section area is perpendicular to the velocity which is a.
00:49
Now assume that every drop she intersects sticks to her.
00:53
At what rate will she accumulate mass and what retarding force will the rain exert on her.
00:59
Great, so this is pretty simple so what you can do is you have to first calculate the volume.
01:10
Volume of rain the athlete is running through per unit time.
01:15
So volume will be equal to the speed times the area with that you need to multiply with the time.
01:29
Because speed has got time by time so the distance times the area will give you the volume swept by the athlete.
01:42
Next you have to calculate number of rain drops in this volume...