A driver is traveling at 90 mi/h down a 3% grade on good, wet pavement. An accident investigation team noted that braking skid marks started 410 ft before a parked car was hit at an estimated 45 mi/h. Ignoring air resistance, and using theoretical stopping distance, what was the braking efficiency of the car?

58.7%

Step-by-step explanation:

First, before calculating the braking efficiency of the car; we need to find the coefficient of the rolling friction of the driving by applying the formula;

where;

V₁ = 90 mi/h

V₁ =    ( since 1 mi = 5280ft and  1 hour is equivalent to 3600 seconds)

V₁ =

V₁ = 132

V₂ = 45 mi/h

V₂ =

V₂ =

V₂ = 66

Substituting both data into the above equation, we have;

Now, to calculate the breaking efficiency of the car ; we apply the formula:

where;

the braking skid (S) = 410 ft

Value for braking mass factor for automobiles = 1.04

Value for Coefficient (β) of the road adhesion for both good and wet pavement = 0.90

Sin ∝ = 3% = 0.03

coefficient of the rolling friction = 0.016735

V₁ = 132 &  V₂ = 66

Substituting our parameters in the above formula, we have;

≅ 0.587

= 58.7%

∴ The braking efficiency of the car = 58.7%

do i do it on a graph?

step-by-step explanation:

option 3 . (5x + 1) - (-10x + 6)

step-by-step explanation:

option 1 :

(4x + 3) + (-9x + 4)

or 4x+3 -9x + 4

or -5x + 7

option 2

(x - 2) - (6x - 9)

or x-2-6x + 9

or -5x + 7

option 3

(5x+ + 6)

or 5x + 1 + 10x -6

or 15x -5

option 4

-4x+2x+7-3x

-7x + 2x + 7

-5x + 7

hence only option 3 did   not satisfy the given simplify expression.