﻿ What does a speedometer record-average speed or instantaneous speed? from Physics Motion in Straight Line Class 11 CBSE
A particle moves in a circular orbit. What is the displacement undergone by the particle in one complete revolution?

Zero.
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A drunkard walking in a narrow lane takes 7 steps forward and 4 steps backward followed by same strokes. Each step is 0.5m long and requires 1sec. Find the net displacement of drunkard in three such strokes and average velocity of the drunkard.

Given, the drunkard walks 7 steps forward and 4 steps backward.

So, the net displacement undertaken by the drunkard = 3 steps in one stroke

Also given, length of 1 step = 0.5 m

Time taken to take 1 step = 1 sec

∴ Displacement in 1 stroke = 3 x 0.5=1.5m

Therefore,

Displacement in 3 strokes = 3 x 1.5 =4.5m

Time taken to walk one step is 1 sec.

Since to complete one stroke, drunkard walks 7 steps forward and 4 steps backward i.e. total of 11 steps, therefore drunkard takes 11s to complete one stroke.

So,

Time taken to complete three strokes, t = 11 x 3 = 33s

Now, average velocity of drunkard is given by,

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# What does a speedometer record-average speed or instantaneous speed?

Instantaneous speed.
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What is rest?

When an object does not change its position with time, with respect to it's surroundings. In such a case the object is said to be at rest.
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What is motion?

When an object changes it's position with time, with respect to it's surroundings, the object is said to be in motion.
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