Explanation:
20 meters is travelled by him
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Answer
Correct Answer is B(to change direct current into alternating current)
Explanation
commutation
The main aim of commutation is to maintain the torque acting on armature of DC motros in the same direction.
commutator a switch which is used to convert the direction of flow of electric current it is connected to the armature of DC motor.
In DC motors, voltage across the armature is alternating in nature. The direction of this current is reverses by Commutator when armature of DC motors passes through magnetic neutral axis to maintain the unidirectional. Hence, commutator is used to change direct current into alternating current.
We will start from the definition of power in terms of the Force. Power could be described as the change of energy in an instant of time. Considering that Energy is the product between the Force and the distance traveled we would arrive at the expression


Here,
F = Force
h = Height
t = Time
As there is no external force, apart from the force of gravity, and this, is constant during the course of the object we will also have to be constant power and therefore this during its course will be the same. The correct answer is (1)
Answer:
Part a)
f = 371.1 Hz
Part b)
f = 417.7 Hz
Part c)
beat frequency = 46.6 Hz
Explanation:
Part a)
Due to doppler's Effect the frequency of the sound heard by the train which is moving away from the observer is given as



Part b)
Now from the second train which is approaching the person we can say



Part c)
As we know that beat frequency is the difference in the frequency from two sources

