Explanation:
Given that,
Frequency of train horn, f = 218 Hz
Speed of train, 
The speed of sound, V = 344 m/s (say)
The speed of the observed person, 
(a) When the train approaches you, the Doppler's effect gives the frequency as follows :

(b) When the train moves away from you, the Doppler's effect gives the frequency as follows :

Hence, this is the required solution.
Answer:
1250 N
Explanation:
length of wrench = 20 cm = 0.2 m
Write the length of wrench in vector form
r = 0.2 j metre
Direction of force= 
Let the magnitude of force is F
So, write the force in vector form
F = F 
torque, T = 150 Nm
Torque = T = r x F

F = 1250 N
Thus, the magnitude of force is 1250 N.
Answer:
d.) Marbles 1 and 2 repel each other, but no interaction occurs with marble
Explanation:
Rubbing the glass against the silk charges the glass positively.
Assuming polarization is ignored,
●Glass won't conduct electrical charge. Therefore, acting as a insulator.
●neutral objects won't distribute it's charge when affected by charge objects in proximity. Therefore, over the marble surface, the charge remain spherically symmetrical (undisturbed)
Marble 1 is positive
Marble 2 is positive
Since marble 1 and 2 are positive, repulsion will occur.
marble 3 is neutral (still assuming polarization is ignored), therefore, no interaction with marble 1 and 2
D is the answer.
Answer:
Image will form at distance 22.22 cm behind the mirror
Explanation:
As we know that the mirror formula is given as

now we know that
object distance from mirror is

Focal length of the mirror is given as

now we have


