Question

brakes stop a train in certain distance d.When braking force is made one-fourth, the brakes will stop the train in a distane

Answer 1

Answer: 4d

Force (F)= mass (m) × acceleration (a)

When the force is made one-fourth, if the mass is same, the acceleration will also reduce by one-fourth.

$a'=a/4$

now using the equation of motion,

$2as=v^2-u^2$

where s is the distance, v is the final velocity, u is the initial velocity and a is the acceleration.

$v=0$ (because the train stops)

$s=d$

$a'=a/4$

we need to find d'

$\frac{d'}{d}=\frac{0-u^2/2a/4}{0-u^2/2a}\\ \Rightarrow d'=4d$

Hence, when braking force is made one-fourth, the brakes will stop the train in a distance 4d.

Answer 2

Answer:

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