Question

Fa automolile
[
begin{array}{l}
V^{2}=u^{2}-2 a b
therefore u_{1}^{2}-2 a s=0
u_{1}^{2}=2 a b_{1}
end{array}
]
Fa car
[
u_{2}^{2}=2 a s_{2}
]
[
begin{array}{l}
left(frac{u_{2}}{u_{1}}right)^{2}=frac{S_{2}}{s_{1}}
quadleft(frac{120}{60}right)^{2}=frac{s_{2}}{20}
Rightarrow s_{2}=80 mathrm{m}
end{array}
]

# 7. An automobile travelling with a speed of 60 km/h, can brake to stop within a distance of 20 m. If the car is going twice as fast, ie 120 km/h, the stopping distance will be [AIEEE 2004, 4/300)

Solution