Rain Drop

The above is a depiction of rain drops falling on a car being driven at a speed of 3 3 m/s. If the angle of the rain drops on the car window is exactly 45 45 °, then what is the speed of the rain drops from a stopped observer's position? (Assume that the speed of the rain drops is constant and raindrops are falling straight down.)

2 \sqrt{2} m/s 3 m/s 2 m/s 3 \sqrt{3} m/s

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36 solutions

tan 45 = velocty of rain / velosty of car

wrong....tan 45 = (velocity of car / velocity of rain)...just coincident that the rain and car have the same velocity that is why your solution got the right answer... TOA is Tan(x) = Opposite / Adjacent = (Opposite of angle 45 is velocity of the car)/ (Adjacent of angle 45 is the velocity of the rain)

DFran Von - 7 years, 3 months ago

why we ta ke tan angle only ?

lalita verma - 7 years, 3 months ago

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Becoz only the tan angle helps to get the answer.......

kiran kumar p - 7 years ago

velocity of car .

Taimoor Afzal - 7 years, 3 months ago

wrong

Ronard Paña - 7 years, 3 months ago

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why wrong!!

Gerryvee Aseñas - 7 years, 2 months ago
Deano Damario
Mar 2, 2014

t a n 45 = V r a i n V c a r 1 = V r a i n 3 V r a i n = 3 tan { 45\quad =\quad \frac { Vrain }{ Vcar } } \\ 1\quad =\quad \frac { Vrain }{ 3 } \\ Vrain\quad =\quad 3\quad ㎧

(Y)

farah nabila nasution - 7 years, 3 months ago

wrong....tan 45 = (velocity of car / velocity of rain)...just coincident that the rain and car have the same velocity that is why your solution got the right answer... TOA is Tan(x) = Opposite / Adjacent = (Opposite of angle 45 is velocity of the car)/ (Adjacent of angle 45 is the velocity of the rain)

DFran Von - 7 years, 3 months ago

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It is not coincident that the velocity of the car and the rain are same---the angle is 45 degrees so they are the same

Dhananjay S Mantri - 7 years, 3 months ago
Rahul Meena
Mar 1, 2014

tan(45)=v/3 so v = 3*tan(45)=3 m/s

wrong....tan 45 = (velocity of car / velocity of rain)...just coincident that the rain and car have the same velocity that is why your solution got the right answer... TOA is Tan(x) = Opposite / Adjacent = (Opposite of angle 45 is velocity of the car)/ (Adjacent of angle 45 is the velocity of the rain)

DFran Von - 7 years, 3 months ago
Kavya Kammana
Mar 4, 2014

tan45-= 1= 3/x therefore x= 3m/s

oh I missed that!

Vignesh Kumar - 7 years, 3 months ago
José Bezerra
Mar 2, 2014

An observer in the reference frame of the window, which is moving at a constant speed of 3 m / s see the raindrops falling in a direction that is 45 ° to the vertical (or horizontal). So the sum vector car speeds, and rain should form a rectangle and an isosceles triangle, where the speed vectors are the legs. Therefore, for a reference outside the car the rain must fall vertically with a speed of module 3 m / s...

Um observador no referencial da janela, que está se movendo a uma velocidade constante de 3 m/s vê as gotas de chuva caindo em uma direção que faz 45° com a vertical (ou horizontal). Logo a soma das velocidades vetoriais do carro e da chuva devem formar um triângulo retângulo e isósceles, onde os vetores velocidades são os catetos. Logo, para um referencial fora do carro a chuva deve cair verticalmente com uma velocidade de módulo 3 m/s.

Lalita Verma
Mar 13, 2014

this question is wrong.because question says that rain fall on car is 45 angle but in bracket given that rain fall straight down. secondly question asked that what is speed of rain but in bracket given that assume speed of rain is constant.how this possible???????

Arijit Banerjee
Mar 9, 2014

tan 45 = |velocity of car|/|velocity of rain| ... so answer is 3m/s ( ' | | ' means the mod value of the velocity)

3

Zain Ashfaq
Mar 9, 2014

TAN45=V/3 (TAN45=1) 1=V/3 V=3

Vinit Sharma
Mar 8, 2014

3m/s

the answer is like this : tan(45) = 1 then. tan(45) *3=3m/s

Anil Kumar Neela
Mar 7, 2014

tan45=vel of rain/vel of car

:)

Falak Naz
Mar 7, 2014

tan45=velocity of car/velocity of rain drop (velocity of car is 3m/s and rain is x )so tan 45=1,1=3/x ,=3m/s

Hi, I think its tan45=x/3.

Jodi Jr. Ambid - 7 years, 3 months ago
Pawan Jangid
Mar 6, 2014

v=u+at; v=0,u=30; then t=3.06 tatal time required T=6.12

??????? i think this was not the required solution!

Arijit Banerjee - 7 years, 3 months ago
Niaz Khan
Mar 6, 2014

IT shuold b 3 m/s

Pavel Ahmed
Mar 5, 2014

It's ok if , tan 45 degree = Velocity of rain / Velocity of car = 1 ; The velocity of rain = The velocity of car = 3 m/s.

what about if , There is a Right triangle whose angles are : 90 degree , 45 degree & 45 degree . so Opposite side ( the velocity of rain) = Adjacent side ( the velocity of the car ) = 3 !

tan 45 = (velocity of car / velocity of rain)...just coincident that the rain and car have the same velocity that is why your solution got the right answer... TOA is Tan(x) = Opposite / Adjacent = (Opposite of angle 45 is velocity of the car)/ (Adjacent of angle 45 is the velocity of the rain)

DFran Von - 7 years, 3 months ago
Shahida Afzal
Mar 5, 2014

the ans is 3 m/s

Shubham Dhingra
Mar 5, 2014

Direction of rain with respect to car is given by : tan45= Vel. of Rain/ Vel. of Car 1=x/3 (say 'x' be velocity of rain) Therefore, x=3

tan 45 = Velocity of rain/Velocity of car

Amer Iliyas
Mar 4, 2014

if v is vel of rain, then tan45 =v/3, or v = 3 * tan45 = 3 * 1 =3.

Sai Mallesh
Mar 4, 2014

since its clearly mentioned to assume the rain drops fall straight down thus we take tan angle thus tan45=velocity of rain drops/3 = 3m/s

Saurabh Yadav
Mar 4, 2014

tan 45=velocityof drop downward/velocity of car....... tan45=x/3...... x=3

Ahsan Khan
Mar 4, 2014

tan45=Vrain/Vcar => 1=Vrain/3 =>1*3=Vrain, or Vrain=3 m/s

Bharati Kumbar
Mar 4, 2014

tan(45)=v/3 so v = 3*tan(45)=3 m/s

Kash If
Mar 3, 2014

tan45=x/3 1=x/3 3=x

tan45= V rain/ Vcar

By Right Angled Triangle, tan = OPP Side/ADJ Side i.e., tan 45 = rain drop speed/ car speed 1 = x/3 from these x=3

Aravind Raj
Mar 2, 2014

tan45= velocityof rain(Vr)/ velocity of car(Vc) 1=Vr/Vc 1=Vr/3 Vr=3

Asif Iqbal
Mar 2, 2014

The above problem has solution = 3 m/s

3 m/s

Syed Abbas - 7 years, 3 months ago
Dewan Masood
Mar 2, 2014

tan 45 = (velocty of rain) / (velosty of car)

Right 45-45-90 vector triangles, anyone?

Cawerdo San
Mar 1, 2014

The window is oblique not the rain ever ..

Krishna Garg
Feb 25, 2014

Since rain falling straight will make a issocelous triangle having 45 degree angle. iIt has 90 degree anle on screen of car. speed of car is 3 miles/sec , so base of triangle is 3,and hight of rtriangle will be 3 ( isocellous trianle).therefore,Answer is 3

Kajal Choudhary
Feb 22, 2014

If speed of rain is r then tan 45=3/r => r = 3 m/s

Isn't it supposed to be 3 2 3 \sqrt{2} ?

it can be resolved by a triangle, so tan(45)=v/3 so v = 3*tan(45)=3 m/s

Reda Karam - 7 years, 3 months ago

i think it should be 3(sqrt.2)

Raja Shekhar Kollapudi - 7 years, 3 months ago

Why?

Micah Wood - 7 years, 3 months ago

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