Question

Need explanation and correct answer
Topic Motion
Class 9th

The motion of an object is described by the velocity-time graph shown in the figure given below. The average speed of object for the entire journey is

a)Zero
b)9 m/s
c)12 m/s
d)16 m/s ​

Answer 1

Answer:

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So to find the position of the object at time 20 second, we draw a line parallel to y-axis from time 20 and take the point where it intersects then again draw a line parallel to the x-axis, we get the distance where it intersects the y-axis.

Here the position is 8 meters from starting.

ii) Distance travel in 12 seconds by the object is 6 meters.

iii) Since average speed of object is define as total distance covered by object by total time take. So here total distance is 8 m and the total time is 20 second,

Average speed =

= 12 m/s

Answer 2

Explanation:

Answer:

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A

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swer

7+4 3

5+2 3

=a+b 3

Since rationalization of c+ d a+b = c+ d a+ b × c− dc− d

Taking L.H.S.

By rationalization,

7+435+23

= 7+4 3 5+2 3 × 7−4 7−4 3

Since, {(a+b)(a−b)=a 2 −b 2 }

= [(7) 2 −(43 ) 2 ](5+2 3 )×(7−4 3 )

= 49−16 33

35+14

3 −20 3 −8 33

= 49−4835− 3

(14−8)−24

= 135− 3 (6)−24 =11−6 3

Hence, by comparing a = 11 & b = -6.