Answer:
81.47°
Explanation:
The forward force on the tire is the horizontal component of its weight along the incline mgcosФ. The frictional force along the incline is μmgsinΦ where mgsinΦ is the vertical component of the tire's weight along the incline.
Since the tire rolls without slipping, then
mgcosФ = μmgsinΦ where μ = coefficient of kinetic friction = 0.15 (since the tire is in motion) and Φ is the angle of the incline.
So, mgcosФ = μmgsinΦ
mgcosФ/mgsinΦ = μ
μ = cosФ/sinΦ
μ = 1/tanФ
tanФ = 1/μ
Φ = tan⁻¹(1/μ)
substituting into the equation, we have
Φ = tan⁻¹(1/0.15)
Φ = tan⁻¹(6.667)
Φ = 81.47°