Question

(a) Identify the following graphs and answer the questions :
(i) Which of the graphs indicates negative acceleration ? Why ?
(ii) What do you infer from the graph in which velocity-time graph is parallel to the time axis ?
(iii)Which of the graphs represents a body moving with initial velocity not equal to zero, but with constant acceleration ? Justify your answer.
(b) A bus starting from rest moves with a uniform acceleration of 0.1 M/S2 for 2 minutes. Find :
(i) the speed acquired
(ii) the distance travelled.

CBSE Class IX Science LA (5 Marks)

Answer 1

(a) (i) Graph I; since velocity decreases with time.     

(ii)   Graph II; since velocity is constant, the acceleration of the body is zero.                             

(iii) Graph III; since the velocity-time graph does not pass through the origin.                         
(b) u = 0, a = 0.1 mis² t = 2 min = 120 s. speed acquired v =? distance travelled s = ?

(i)   As,                                              v = u + at
                                                    v = 0 + 0.1 x 120

                                                       = 12 m/s

(ii) As                                               s = ut + —1 ate

                                           0 + (0.1 x 120 x 120)/2

                                                 = 720 m

Answer 2

(a) (i) Graph I; since velocity decreases with time.

(ii)

Graph II;

since velocity is constant, the acceleration of the body is zero.

(iii) Graph III; since the velocity-time graph does not pass through the origin.

(b) u = 0, a = 0.1 mis² t = 2 min = 120 s. speed acquired v =? distance travelled s = ?

(i) As, v

= u + at

v = 0 + 0.1 x 120

= 12 m/s

(ii) As s = ut + —1 ate

0 + (0.1 x 120 x 120)/2

= 720 m