For optimum speed, v‌opt ‌=√rg‌tan‌θ where θ=45∘ ‌vopt=√rg‌tan‌45∘ ‌vopt=√rg‌‌...‌ (ii) ‌ From Eq. (i), (vmax)2‌=‌
(vopt)2(tan‌θ+µ)
1−µ‌tan‌θ
(2vopt)2‌=‌
(vopt)2(tan‌θ+µ)
1−µ‌tan‌θ
⇒4(1−µ)‌=1+µ 4−4µ‌=1+µ⇒3=5µ µ‌=0.6 The coefficient of static friction between the wheels of the car and the road is 0.6 .
