relativ velosity?

Question

a man is walking with a speed of 2km/h. the rain apears to him vertically downwards. when he doubles the speed rain apears to him making an angle of 30 with the vertical.find the velocity of rain

Answer 1

4/x = tan 30

x = 4sqrt(3) m/s.

Answer 2

From the point O drop down a vertical line to a point P.

At P draw a horizontal line.

From O draw a line at an angle 30 degree to the vertical and prolong it to meet the horizontal at Q.

Mark R to the left of P such that PQ = PR denoting PR = 4km/h.

Join OR.

OQ represents the rains velocity.
OP represents the resultant when the man's speed is 2km/h
OR represents the resultant, when the man's speed is 4km/h.

The triangle formed is an equilateral triangle with each side equal to 4 km/h.

Therefore the rain's speed is 4km/h.

Answer 3

You do have your answers.

"Dr.Shafer" is correct but a parallelogram of the velocity will be easier to understand, draw it to largest possible scale.

Hint for calculation by mathematical method:

1. In a 30- 90-60 degree triangle hypotenuse is 2 times the smallest side.

2. A 3-4-5 right angle triangle can be used as the key to simplification.

Answer 4

To calculate velocity of a mass flux coming on the vertical ,it is needed to know the angle of aberration and the velocity of the observer.
Velocity of the rain= 2km/hr x2 x Tan 30 = 2.305 km/hr

Answer 5

so when he doubles his speed,he will have speed 4kmph.
rain appears to him at an angle of 30.
tan30=velocity of rain/velocity of man
1/(root)3=VR/4
VR=4/root3

Answer 6

when the man doubles his speed,it now becomes 4km/h,
using cos30
=adjacent/hypothenus
=(4km/h)/velocity of rain
therefore velocity of rain,
=4/cos30 km/h

Answer 7

Might try Pythagoras for this one.