(Q) Choose the correct option(s) regarding acceleration of the particle :
(A) acceleration of particle at t=1.5 sec is 4 m/s^-2.
(B)acceleration of particle at t=3.5 sec is -4 m/s^-2.
(C) acceleration of particle from t=1 sec to t=3 sec is constant but non-zero.
(D) acceleration of particle from t=1 sec to t=3 sec is constant.

The velocity time graph of a particle moving along a straight line is shown in the figure. In the time interval from t = 0 to t = 8 second, answer the following three questions.
Graphic

Dear Student,


We know that, slope of V-T graph gives the acceleration. 
So, 
Slope = Final velocity - initial velocitytime taken 

Case 1, acceleration of particle at t=1.5 sec

It is evident from the graph that at 1.5 s, the graph has straight line. Thus, there is no change in the velocity. 
The inst. acceleration will be 0 m/s2. Thereofore, it is wrong statement.

Case 2, acceleration of particle from t=1 sec to t=3 sec is constant but non-zero.
This statement is false, as when there is no change in velocity then the acceleration would be 0 (as it is both a constant and zero).
​​​​​​
Case 3, acceleration of particle at t=3.5 sec is -4 m/s^-2.
If see logically, the instantenous acceleration at 3.5 s will be a negative value but, we can not actually compute the value being graph is not upto scale. Also, numerical value 4 is not so accurate (say for example if the change in velocity is - 0.5 m/s and t = 3.5 s the a = - 0.14 m/s2) Thus, this statement is also false.

Case4,  acceleration of particle from t=1 sec to t=3 sec is constant.
This statement is true. As in this the acceleration is 0 m/s2, which is constant number.


​​​​Therefore, option 'D' is correct.





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