a mountain biker cycling a trail traveling at 5.4 m/s begins to slow down when she notice a wooden bridge ahead has flooded. if she begins braking when she is 15.0 m from the bridge and comes to a stop just before reaching the bridge, how long did it take her to stop ?

In order to calculate the time interval taken by the mountain biker to come to a stop, we will use third equation of motion and first find the deceleration:

2as = Vf² - Vi²

where,

a = deceleration = ?

s = distance = 15 m

Vf = Final Velocity = 0 m/s

Vi = Initial Velocity = 5.4 m/s

Therefore,

2a(15 m) = (0 m/s²) - (5.4 m/s)²

a = - 0.972 m/s²

Now, we use 1st equation of motion:

Vf = Vi + at

therefore,

0 m/s = 5.4 m/s + (-0.972 m/s²)(t)

t = (5.4 m/s)/(0.972 m/s²)

t = 5.56 s

andromache andromache · Answer 2 · 2022-03-15T15:14:26+01:00

The time taken should be t = 5.56 s

Calculation of the time taken:

here we used the third equation of motion

But first we determine the deceleration.

We know that

2as = Vf² - Vi²

here,

a = deceleration = ?

s = distance = 15 m

Vf = Final Velocity = 0 m/s

Vi = Initial Velocity = 5.4 m/s

So,

2a(15 m) = (0 m/s²) - (5.4 m/s)²

a = - 0.972 m/s²

Now, we use 1st equation of motion:

So,

Vf = Vi + at

0 m/s = 5.4 m/s + (-0.972 m/s²)(t)

t = (5.4 m/s)/(0.972 m/s²)

t = 5.56 s

Hence, The time taken should be t = 5.56 s

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