Physics, 27.09.2020 14:01 kim3265

A motorist traveling at 17 m/s encounters a deer in the road 39 m ahead. If the maximum acceleration the vehicle’s brakes are capable of is −7 m/s 2 , what is the maximum reaction time of the motorist that will allow her or him to avoid hitting the deer? Answer in units of s. 019 (part 2 of 2) 10.0 points If his or her reaction time is 1.21983 s, how fast will (s) he be traveling when (s)he reaches the deer? Answer in units of m/s.

Answers: 3

Show answers

Answers

Answer from: jdkrisdaimcc11

1. t_reaction = 1.08 s

2. v₀₁ = 16.365 m/s

Explanation:

1. This is a kinematics exercise, let's analyze the situation a bit, we can calculate the braking distance and the rest of the distance we can use to calculate the reaction time.

Braking distance

v² = v₀² + 2 a x

when he finishes braking the speed is v = 0

0 = v₀² + 2 a x

x = -v₀² / 2a

x = - 17²/2 (-7)

x = 20.64 m

the distance for the reaction is

d = x_reaction + x

x_reaction = d - x

x_reaction = 39 - 20.64

x_reaction = 18.36 m

as long as it has not reacted the vehicle speed is constant

v = x_reaction / t_reaction

t_reaction = x_reaction / v

t_reaction = 18.36 / 17

t_reaction = 1.08 s

2. Let's find the distance traveled in the reaction time of t1 = 1.21983 s

as the speed is constant

v = x / t

x₁ = v t₁

the distance traveled during braking is

v² = v₀² + 2a x₂

0 = v₀² + 2 a x₂

x₂ = -v₀² / 2a

v = v₀

the total distance is

x_total = x₁ + x₂

x_total = v₀ t₁ + v₀² / 2a

39 = v₀ 1.21983 + v₀²/14

v₀² + 17.08 vo - 546 =0

we solve the second degree equation

v₀ = [ -17.08 ±√(17.08² + 4 546) ]/2

v₀ = [-17.08 ± 49.81 ]/2

v₀₁ = 16.365 m/s

v₀₂ = - 33.445 m/s

as the acceleration is negative the correct result is v₀₁ = 16.365 m/s

Answer from: Quest

Is a vector quantity that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.

Answer from: Quest

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this