Chapter 2 - Kinematics: Description of Motion - Learning Path Questions and Exercises - Exercises - Page 62: 37

The driver CANNOT beat the event. $a_{min}=9.9 m/s^{2}$

$v^{2}=u^{2}+2aS$ $v^{2}=0+2\times 9 \times 100=1800$ Now, $v=u+at=0+9t=9t$ Hence, $81t^{2}=1800$ or, $t=4.71s$ But the time to beat the event is 4.5 s. So, the driver CANNOT beat the event. $v=0+a\times 4.5=4.5a\, m/s$ $(4.5a)^{2}=u^{2}+2aS=0+200a$ $a=9.9 m/s^{2}$ So, minimum acceleration to beat the event is $9.9 m/s^{2}$