An engineer in a locomotive sees a car stuck
on the track at a railroad crossing in front of
the train. when the engineer first sees the
car, the locomotive is 270 m from the crossing
and its speed is 12 m/s.
if the engineer’s reaction time is 0.79 s,
what should be the magnitude of the minimum deceleration to avoid an accident?
answer in units of m/s
2
.

a=0.27637 m/s²

Explanation:

Hello,

You should remember that ;

Stopping distance=reaction distance + braking distance

First find the reaction distance which is that distance traveled from point of detecting danger to start of breaking process.

Formula: d=(s*r) where s is speed in m/s and r is reaction time in seconds

Given: s=12m/s  and r=0.79 s

d= 12*0.79=9.48 m

Remaining distance to cover and stop

Where distance from locomotive to railroad crossing is 260, then remaining distance will be;

270m-9.48m=260.52 m

To get magnitude of minimum deceleration to avoid an accident you apply the formula:

v²=u²-2as

where

v= final speed = 0 m/s

u=speed of locomotive = 12 m/s

a=acceleration in m/s²

s=remaining distance to cover

v²=u²-2as

0²=12²-2*a*260.52

0=144-521.04 a

144/521.04= 521.04/521.04a

a=0.27637 m/s²

Hope this Helps!

the entire statement is true and correct.  

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electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia