Question

Q.11 Rain drops fall vertically at a speed of 20 ms. At what angle do they fall on the wind screen of a car moving with a velocity of 15 ms-1 , if the wind screen velocity inclined at an angle of 23° to the
vertical?
cot -1 (4 / 5) = 36
(a)60°
(b)30°
(c) 45 °
(d) 90°​

Answer 1

Explanation:

Hint: Speed is defined as the distance covered per unit time and speed is a scalar quantity. SI unit of speed is ms−1 . Displacement is defined as the process in which objects' positions are changed and in displacement the initial position of objects are changed. Displacement is also defined as change in initial position of objects to the final position and displacement is denoted as S.

Complete step by step solution:

Velocity is defined as the rate of change of displacement with respect to time and in kinematics velocity is a fundamental concept.SI unit of velocity is ms−1 Velocity tracking is the measure of velocity.

Velocity (v) =ΔSΔt

The dimensional formula of velocity is M0L1T−1.

From the data

Velocity of rain( vr )=-20j

Velocity of car (vc )=15i

Therefore the velocity of rain with respect to car (v ) = vr−vc

v=−20j−15i

Angle made by rain (θr wrt wind screen is given as:

θr=θ+230

From the data the value of θ=370

After substituting these value in the above equation

We get θr=600

So the rain will fall at 600 on the wind screen

The correct option is A.

Note: When you are moving in a car the raindrop appears to the moving towards you, but that is actually because you are moving towards you, but that is actually because you are moving towards it, in the same way that trees appear to be moving in the opposite direction to you if you look out of the side window.