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Toy Car: Actual translational speed of the car; angular velocity of the flywheel

When a toy car is rapidly scooted across the floor, it stores energy in a flywheel. The car has mass 0.180g, and its flywheel has a moment of inertia of 4.00*10^(-5)kg.m^2. The car is 15.0cm long. An advertissement claims that the car can travel at a scale speed of up to 700km/h (440mi/h). The scale speed is the speed of the toy car multiplied by the ratio of the length of an actual car to the length of the toy. Asuume a length of 3.0m for a real car.

a) For a scale speed of 700km/h, what is the actual translational speed of the car?

b) If all the kinetic energy that is initially in the flywheel is converted to the translational kinetic energy of the toy, how much energy is originally stored in the flywheel?

c) What initial angular velocity of the flywheel was needed to store the amount of energy calculated in part b) ?

Solution Preview

)
Vc = speed of actual car, Vm = speed of model car
Lc = Length of actual car, Lm = Length of model car

Vm = Vc*Lm/Lc = 700*0.15/3 = 35 km/hr = 9.722 ...

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