Answer:
Explanation:36.05 km
Given
First car travels
South
then turns and travels
east
Suppose south as negative y axis and east as positive x axis
So, 

Displacement is the shortest between initial and final point
Dispalcement
Displacement
Displacement
Magnitude 
Magnitude
Answer : The frequency decreases by a factor of 2.
Explanation :
Given that the wave travels at a constant speed. The speed of the wave is given as :

Where
υ is the frequency of the wave
and λ is the wavelength of the wave.
In this case, the speed is constant. So, the relation between the frequency and the wavelength is inverse.

If the wavelength increases by a factor of 2, its frequency will decrease by a factor of 2.
Hence, the correct option is (A) " The frequency decreases by a factor of 2 ".
Explanation:
Let the speeds of father and son are
. The kinetic energies of father and son are
. The mass of father and son are 
(a) According to given conditions, 
And 
Kinetic energy of father is given by :
.............(1)
Kinetic energy of son is given by :
...........(2)
From equation (1), (2) we get :
..............(3)
If the speed of father is speed up by 1.5 m/s, so the ratio of kinetic energies is given by :


Using equation (3) in above equation, we get :

(b) Put the value of
in equation (3) as :

Hence, this is the required solution.
Question four bulbs A,B,C and D are connected in a circuit shown in the figure below, the letters X, Y and Z represent three switches. Which switch is used to operate switch A separately?
Answer: x