Question

A car with vertical windshield moves along in a rain storm at a speed of 40 km per hour The Rain drops fall vertically with the terminal speed of 20 m per second the angle at which the raindrops strike the windshield is

Answer 1

Answer:

Angle, ∅= tan⁻¹ (5/9)

Explanation:

[Refer to the attached image 1 to better understand the scenario and visualize it]

Given;-

      Velocity of Car, Vc = 40 km/h

                                      = 40 × 5/18 m/s

                                      = 100/9 m/s

     Velocity of Rain (Vertically), Vr= 20 m/s

Let, the angle to be found be '∅'.

Now;-

Assuming the car to be at rest, the velocity of car gets added to that of rain but with opposite direction.

[Refer to attached image 2 to better visualize it]

Now, if we quite observe the sides around ∅, we get a rough idea that tan function can help us get our angle. So,

               tan∅ = Vc/ Vr

               tan∅ = 100/9 /20

               tan∅ = 100/9×20

               tan∅ = 5/9

                    ∅ = tan⁻¹(5/9)

Therefore, the angle at which the rain drops strike the windshield is tan⁻¹(5/9).

Hope it helps ;-))