Answer:
Answer: b. 20.8 ft-lb
Step-by-step explanation:
Step-by-step explanation:

Area = pi*r^2
Circumference = 2pi*r
Step 1: find the radius from area
81pi=pi*r^2
81=r^2
9=r
Step 2: plug in radius to the circumference equation
Circumference = 2pi*r
18pi is the answer, otherwise know as 56.52 as well.
Answer:
37 mph
Step-by-step explanation:
Sum of forces on the car in the y direction:
∑F = ma
N − mg = 0
N = mg
Sum of forces on the car in the x direction:
∑F = ma
-Nμ = ma
-mgμ = ma
-gμ = a
Given μ = 0.75 and g = 32 ft/s²:
a = -(32 ft/s²) (0.75)
a = -24 ft/s²
Use kinematics to find the initial velocity.
v² = v₀² + 2aΔx
(0 ft/s)² = v₀² + 2 (-24 ft/s²) (60 ft)
v₀ ≈ 53.7 ft/s
v₀ ≈ 37 mph
(2,5) (3,-) do not quote me on it but I think that’s wrong