Question
A train approaches a stationary observer with a speed of
36 km/h. It emits a sound of frequency 500 Hz. If the speed of sound is 340 m/s, what is the apparent frequency heard by the observer?Solution
The apparent frequency (f′) heard by a stationary observer when a source is moving towards them is given by the Doppler effect formula: 
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How many persons are sitting between O and R?
How many persons are sitting between S and D when counted from left of D?
How many person sit between tallest person and shortest person?
Who likes Daisy?
How many persons are sitting between O and N when counted from the left of O?
Four of five are same in such a way that they form a group. Which of the following doesn’t belong to the group.
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How many persons are sitting between D and C when counted from the left of D?
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