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Class 11
Physics
Motion in a straight Line
a three wheeler starts from rest accelerates unif...

Question:
A three-wheeler starts from rest, accelerates uniformly with 1 m s^–2 on a straight road for 10 s, and then moves with uniform velocity. Plot the distance covered by the vehicle during the nth second (n = 1,2,3….) versus n. What do you expect this plot to be during accelerated motion: a straight line or a parabola?

Answer:

Straight line

Distance covered by a body in nth second is given by the relation

D_n = u + a/2(2n-1) .... (1)

u = Initial velocity

a = Acceleration

n = Time = 1, 2, 3, ..... ,n

In the given case,

u = 0 and a = 1 m/s²

∴ D_n = 1/2(2n-1) .... (2)

This relation shows that:

D_n ∝ n … (iii)

Now, substituting different values of n in equation (iii), we get the following table:

n	1	2	3	4	5	6	7	8	9	10
D_n	0.5	1.5	2.5	3.5	4.5	5.5	6.5	7.5	8.5	9.5

The plot between n and Dn will be a straight line as shown:

Since the given three-wheeler acquires uniform velocity after 10 s, the line will be parallel to the time-axis after n = 10 s.

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