Motion in a Straight Line
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Question : 23
Total: 27
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?
Solution:
Initial velocity, u = 0 , a = 1 m s – 2 , t = 10 s , If S n be the distance covered by the three-wheeler in nth second. Then
S n = u +
( 2 n − 1 ) ,
S n =
( 2 n − 1 ) =
( 2 n − 1 )
Forn = 1 ,
S 1 =
( 2 × 1 − 1 ) = 0.5 m
n = 2 ,
S 2 =
( 2 × 2 − 1 ) = 1.5 m
n = 3 ,
S 3 =
( 2 × 3 − 1 ) = 2.5 m and so on
The following is the table for the distanceS n t h travelled in n t h second.
D n = distance covered by the particle in 10 sec.
D n = u n +
a n 2
= 0 × 10 + 1 2 × 1 × 10 2
( n = 10 )
= 50 m .
As the equation describing the relation betweenD n and n is of seconddegree, so the graph of the vehicle from start to 10t h second is expectedto be a parabola. Velocity of the vehicle at the end of 10t h second isv = 0 + 1 × 10 = 10 m s – 1 and it will move with this velocity after 10 seconds.Thus the graph will be a straight line inclined to time axis for uniformlyaccelerated motion. The plot of the distance covered by the three wheelerwith time is shown in the graph.
For
The following is the table for the distance
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| 0.5 | 1.5 | 2.5 | 3.5 | 4.5 | 5.5 | 6.5 | 7.5 | 8.5 | 9.5 |
Also
As the equation describing the relation between
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