Answer:
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%