Question

A highway curve with radius R = 274 m is to be banked so that a car traveling v = 25.0 m/s will not skid sideways even in the absence of friction. At what angle should the curve be banked? 2. what is the correct equation for the sum of the forces in the x direction? What is the correct equation for the sum of the forces in the y direction? A. ΣFx:−Nsinθ=mv2/R; ΣFy:Ncosθ−mg=0 B. ΣFx:−Ncosθ=−mv2/R; ΣFy:Nsinθ−mg=0 C. ΣFx:Nsinθ=mv2/R; ΣFy:Ncosθ+mg=0 D. ΣFx:−Nsinθ=mv2/R; ΣFy:Ncosθ=0 E. ΣFx:−Nsinθ=−mv2/R; ΣFy:Ncosθ−mg=0

Answer 1

Answer:

A)   θ = 13.1º  , B)  E

Explanation:

A) For this exercise, let's use Newton's second law, let's set a reference frame where the axis ax is in the radial direction and is horizontal, the axis y is vertical.

In this reference system the only force that we must decompose is the Normal one, let's use trigonometry

        sin θ = Nₓ / N

        cos θ = $N_{y}$ / N

        Nₓ = N sin θ

       Ny = N cos θ

x-axis (radial)

        Nₓ = m a

where the acceleration is centripetal

         a = v² / R

we substitute

        -N sin θ = -m v² / R                   (1)

the negative sign indicates that the force and acceleration towards the center of the circle

y-axis (Vertical)

          Ny - W = 0

           N cos θ = mg

           N = mg / cos θ

we substitute in 1

          mg / cos θ  sin θ = m v² / R

          g tan θ = v² / R

          θ = tan⁻¹ (v² / gR)

we calculate

        θ = tan⁻¹ (25² / 9.8 274)

        θ = 13.1º

B) when comparing the equations the correct one is E