 # Circular Motion and SF=ma

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Circular Motion and SF=ma

Figure 6.5  (a) The force of static friction directed toward the center of the curve keeps the car moving in a circular path. (b) The free-body diagram for the car. Fig. 6.5, p.154

8. The cornering performance of an automobile is evaluated on a skidpad, where the maximum speed that a car can maintain around a circular path on a dry, flat surface is measured. Then the centripetal acceleration, also called the lateral acceleration, is calculated as a multiple of the free-fall acceleration g. The main factors affecting the performance are the tire characteristics and the suspension system of the car. A Dodge Viper GTS can negotiate a skidpad of radius 61.0 m at 86.5 km/h. Calculate its maximum lateral acceleration.

A Dodge Viper GTS can negotiate a skidpad of radius 61.0 m at
86.5 km/h. Calculate its maximum lateral acceleration. Figure 6.5  (a) The force of static friction directed toward the center of the curve keeps the car moving in a circular path. (b) The free-body diagram for the car. Fig. 6.5, p.154

18. A kg object is swung in a vertical circular path on a string m long. If its speed is 4.00 m/s at the top of the circle, what is the tension in the string there?

Consider a conical pendulum with an 80. 0-kg bob on a 10
Consider a conical pendulum with an 80.0-kg bob on a 10.0-m wire making an angle of 5.00 with the vertical (Fig. P6.9). Determine (a) the horizontal and vertical components of the force exerted by the wire on the pendulum and (b) the radial acceleration of the bob. Figure 6.4   The conical pendulum and its free-body diagram. Fig. 6.4a, p.153

Motion in accelerated reference frames
The key idea of General Relativity, called the Equivalence Principle, is that gravity pulling in one direction is completely equivalent to an acceleration in the opposite direction. (A car accelerating forwards feels just like sideways gravity pushing you back against your seat. An elevator accelerating upwards feels just like gravity pushing you into the floor. Alan Lighman

Figure 6.13  A small sphere suspended from the ceiling of a boxcar accelerating to the right is deflected as shown. (a) An inertial observer at rest outside the car claims that the acceleration of the sphere is provided by the horizontal component of T. A kg object is suspended from the ceiling of an accelerating boxcar as in Figure If a = 3.00 m/s2, find (a) the angle that the string makes with the vertical and (b) the tension in the string. Fig. 6.13a, p.161

Figure 6.13  A small sphere suspended from the ceiling of a boxcar accelerating to the right is deflected as shown. (b) A noninertial observer riding in the car says that the net force on the sphere is zero and that the deflection of the cord from the vertical is due to a fictitious force Ffictitious that balances the horizontal component of T. A kg object is suspended from the ceiling of an accelerating boxcar as in Figure If a = 3.00 m/s2, find (a) the angle that the string makes with the vertical and (b) the tension in the string. Fig. 6.13b, p.161

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