The velocity - time graph of an ascending passenger order lift is given in figure. What is the acceleration of the lift:
(i) during the first two seconds ,
(ii) between 2nd and `10 th` second,
(iii) during the last two seconds. .

Explanation

(i) For motion during the first two seconds ,
change of velocity ` = 4.6 - 0 = 4.6 m//s`
time taken ` = 2 - 0 = 2 s`
Thus , acceleration `= ("change of velocity")/("time taken")`
` = ( 4.6)/( 2) = 2.3 m//s^(2)`
(ii) For motion between ` 2nd` second and `10 th` second ,
change of velocity ` = 4.6 - 4.6 = zero`
time taken `= 10 - 2 = 8 s`
Thus , acceleration `= ("change of velocity")/("time taken") = ( 0) /( 8) = zero`
(iii) For motion between `10 th` sec to `12 th` second , change of velocity `= 0 - 4.6 = - 4.6 m//s`
time taken `= 12 - 10 = 2s`
Thus , acceleration ` = ("change of velocity")/("time taken") = ( - 4.6)/( 2) = - 2.3 m//s^(2)`
Negative sign shows retardation