If you are driving at 20 m/s and slam on your brakes and skid at 0.5 g to a full stop,the skidding time in seconds is
A)about 3.
B)about 4.
C)about 5.
D)about 6.
E)more than 6.

Question

Quizplus · Accepted Answer

We can use the following kinematic equation to find the skidding time:

v^2 = u^2 + 2as

where:
v = final velocity (0 m/s)
u = initial velocity (20 m/s)
a = acceleration (-0.5 g or -4.9 m/s^2)
s = distance traveled during skidding (unknown)

Rearranging the equation, we have:

s = (v^2 - u^2) / (2a)

Substituting the given values, we get:

s = (0 - 20^2) / (2 x (-0.5 x 9.81))
s ≈ 40.8 meters

Now, we can use another kinematic equation to find the skidding time:

s = ut + 0.5at^2

where:
t = time (unknown)

Substituting the known values and solving for t, we get:

40.8 = 20t + 0.5(-0.5 x 9.81)t^2
t^2 - 8.16t + 4.08 ≈ 0

Using the quadratic formula, we get:

t ≈ 4.06 seconds

Therefore, the skidding time is about 4 seconds.

If You Are Driving at 20 M/s and Slam on Your