Chapter 4 - Force and Motion - Learning Path Questions and Exercises - Exercises - Page 139: 67

a). $38m$ b). $53m$

m=1500kg speed=90km/hr=25m/s coefficient of friction for dry pavement = 0.85 coefficient of friction for wet pavement = 0.60 a). $a=\frac{coefficient \,of\, friction \,in\, dry\, pavement\, \times mg}{m}=0.85\times9.8=8.3m/s^{2}$ Now, $v^{2}=u^{2}+2aS$ $0=25^{2}-2\times8.3S$ $S=38m$ b). $a=\frac{coefficient \,of\, friction \,in\, wet\, pavement\, \times mg}{m}=0.60\times9.8=5.88m/s^{2}$ Now, $v^{2}=u^{2}+2aS$ $0=25^{2}-2\times5.88S$ $S=53m$