Question

A vehicle moving with 15 km/hr comes to rest by covering 5m distance by applying brakes. If the same vehicle moves at 45 km/hr, then by applying brakes, it will come to rest by covering a distance ______.

Options

• 60 m

• 15 m

• 45 m

• 30 m

Answer 1

A vehicle moving with 15 km/hr comes to rest by covering 5m distance by applying brakes. If the same vehicle moves at 45 km/hr, then by applying brakes, it will come to rest by covering a distance 45 m.

Explanation:

u = 15 km/hr `=(15xx1000)/(60xx60)=150/36` m/s

v² = u² - 2as

`therefore "a"u^2/(2s)=(150xx150)/(36xx36xx2xx5)` m/s²

Next `"s"=u^2/(2a)=45000/(60xx60)xx45000/(60xx60)xx1/2xx(36xx36)/(150xx15)`

= 45 m