An automobile traveling at 70.0 km/h has tires of 75.0 cm diameter. What is the

Question

An automobile traveling at 70.0 km/h has tires of 75.0 cm diameter. What is the angular speed of the tires about their axies? If the car is brought to a stop uniformly in 15.0 complete turns of the tires (without skidding), what is the magnitude of the angular acceleration of the wheels? How far does the car move during the braking? A 1100 kg car has four 16 kg wheels. When the car is moving, what fraction of its total kinetic energy is due to rotation of the wheels about their axles? Assume that the wheels have the same rotational inertia as uniform disks of the same mass and size. Why do you not need to know the radius of the wheels?

Explanation / Answer

15]
(a)
v=70 km/h = 19.44 m/s
r = d/2 = 0.75/2 = 0.375 m

= v / r
= 19.4/(0.375)
= 51.73 rad/s

(b)
² = ² + 2**
= 51.73 rad/s
= 0
= 15*2*pi = 30*pi rad

Substituing Values,

0 = 51.73^2 - 2**30*pi
= -14.2 rad/s^2
(-ve sign means that it is deaccelerating.)
(c)
Distance moved by car,
S = 15*2*pi*r
S = 15 * 2* 3.14 * 0.375 m
S = 35.33 m

please post seperate questions in seperate post.

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