- #1
cpgp
- 14
- 1
- Homework Statement
- A car is fitted with an energy-conserving flywheel, which in operation is geared to the driveshaft so that it rotates at 237 rev/s when the car is traveling at 86.5 km/h. The total mass of the car is 822 kg, the flywheel weighs 194 N, and it is a uniform disk 1.08 m in diameter. The car descends a 1500-m long, 5.00° slope, from rest, with the flywheel engaged and no power supplied from the motor. Neglecting friction and the rotational inertia of the wheels, find (a) the speed of the car at the bottom of the slope, and (b) the angular acceleration of the flywheel at the bottom of the slope.
- Relevant Equations
- T=Ia
I have solved part a using the conservation of energy, getting a (correct) answer of 47.9 km/h, but I am unable to make headway with part b. Based on the flywheel rotating at 237rev/s when the car is moving at 86.5 km/h, I obtained omega = (237*2pi)v/24=62v. Differentiating both sides should give alpha = 62a. But that will yield alpha = 62*g*sin5=53 rad/s^2,when the correct answer is 3.65 rad/s^2.