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A car moving with a speed of 40 km/h can be stopped by applying brakes at least after 2 m. If the same car is moving with a speed of 80 km/h, what is the minimum stopping distance?
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- 8 m
- 6 m
- 4 m
- 2 m
Correct Option: A
v² – u² = 2as
| ⇒ a = | ||
| 2s |
| = | , where u1 = 40 km/h | |
| 2s |
For same retarding force s ∝ u²
| ∵ | = | ⇒ | = |  |  | ² | = 4 | ||||
| s1 | u1² | s1 | 40 |
∴ s2 = 4s1 = 8m
If F is retarding force and s the stopping distance, then 1/2 mv² = Fs
For same retarding force, s α v²
| ∴ | = | | | ² | = | | | ² | = 4 | |||
| s1 | v1 | 40 km/h |
∴ s2 = 4s1 = 4 × 2 = 8m
