A. Conductors. Because in conductors, gap between valence band and conduction band is negligible. Due to this electrons from valence band moves spontaneously to conduction band and on small heating the conductors.
The acceleration of gravity (on Earth) is 9.8 m/s² downward.
This means that every falling object gains 9.8 m/s more downward speed
every second that it falls.
In 5 seconds of falling, it gains (5 x 9.8 m/s) = 49 m/s of downward speed.
If it was already descending at 2.0 m/s at the beginning of the 5 sec,
then at the end of the 5 sec it would be descending at
(2 m/s + 49 m/s) = 51 m/s .
As we know that reaction time will be

so the distance moved by car in reaction time



now the distance remain after that from intersection point is given by

So our distance from the intersection will be 100 m when we apply brakes
now this distance should be covered till the car will stop
so here we will have


now from kinematics equation we will have



so the acceleration required by brakes is -2 m/s/s
Now total time taken to stop the car after applying brakes will be given as



total time to stop the car is given as

Light is faster. Humans can travel faster than sound, however not light- nothing seems to go faster than 3×10∧8 meters per second.