Question

The distance needed to stop a car, d, varies directly as the square of the speed, s, at which it is travelling. A car travelling at a speed of 70 km/h requires a distance of 40 m to make a stop. What distance is required to stop a car travelling at 80 km/h?

Answer 1

Answer:

52.24 km

Step-by-step explanation:

Given that,

The distance needed to stop a car, d, varies directly as the square of the speed, s, at which it is travelling.

d = ks²

Where

k is constant

When s₁ = 70 km/hr, d₁ = 40 m, s₂ = 80 km/hr, d₂ = ?

So,

$\dfrac{d_1}{d_2}=\dfrac{s_1^2}{s_2^2}\\\\d_2=\dfrac{d_1s_2^2}{s_1^2}\\\\d_2=\dfrac{40\times 80^2}{70^2}\\\\d_2=52.24\ km$

So, the new distance is 52.24 km.