Answer:
43.3 m
Explanation:
given :
the initial velocity of the car , u = 20m/s
The reaction time is 0.5s
the distance that the car will travel during the reaction time
= initial velocity x reaction time
= 20 m/s x 0.5 s
= 10 m
Now we turn our attention to the stopping distance AFTER she reacts and steps on the brakes:
recall that one of the forms that the equations of motions can be expressed is:
v² = u² + 2as
where v = final velocity = 0 because the car comes to a stop
u = initial velocity = 20m/s
a = acceleration = -6.0 m/s² (note negative sign because it is a deceleration)
s = distance traveled (we are asked to find this)
substituting the known values into the equation:
v² = u² + 2as
0² = 20² + 2(-6.0) s
0 = 400 - 12s
1.2s = 400
s = 400/12
s = 33.33 m
Total distance travelled
= distance during reacting time + distance while decelerating
= 10 + 33.3
= 43.3 m
