Question

A car travelling at a speed of 30 km h-1 is
brought to halt in 8 m by applying brakes. If
the same car is travelling at 60 km h-1, then
it can be brought to a halt with the same
braking power in
A) 5 m B) 15 m C) 24 m D) 32 m​

Answer 1

Given

A car travelling at a speed of 30 km/h is brought to rest in a distance of 8 m by applying brakes. If the same car is moving at a speed of 60 km/h

To Find

It can be brought to rest with same brakes in

Solution

We know that

$\sf \longrightarrow Fs=\dfrac{1}{2}mv^{2}$

Hence

$\sf \longrightarrow s \propto v^{2}$

Therefore

$\sf \longrightarrow \dfrac{s_{1}}{s_{2}}=\dfrac{v_{1}^{2}}{v_{2}^{2}}$

According to the question

We are asked to find " s₂ "

Therefore

$\sf \longrightarrow s_{2} =s_{1} \times\dfrac{v_{2}^{2}}{v_{1}^{2}}$

Given that

A car travelling at a speed of 30 km/h is brought to rest in a distance of 8 m by applying brakes. If the same car is moving at a speed of 60 km/h

Hence

• s₁ = 30 km/h

• v₁ = 8 m

• v₂ = 60 km/h

Substituting the values

We get

$\sf \longrightarrow s_{2}=8 \times \dfrac{60}{30} \ m$

$\sf \longrightarrow s_{2}=8 \times 4 \ m$

Hence

$\sf \longrightarrow s_{2}=32 \ m$

Therefore

Option (D) is correct

Answer 2

Answer:

Answer is option d : 32 m

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