4. A child has a ball on the end of a cord, and whirlsthe ball in a vertical circle. Assuming the speed ofthe ball is constant (an approximation), when wouldthe tension in the cord be greatest?(a) At the top of the circle.(b) At the bottom of the circle.(c) A little after the bottom of the circle when theball is climbing.(d) A little before the bottom of the circle when theball is descending quickly.(e) Nowhere; the cord is pulled the same amount atall points.

Step 1: Step 2: Step 3: Step 4:

Answered: 4. A child has a ball on the end of a…

Glencoe Physics: Principles and Problems, Student Edition

1st Edition

ISBN:9780078807213

Author:Paul W. Zitzewitz

Publisher:Paul W. Zitzewitz

Chapter7: Gravitation

Section: Chapter Questions

Problem 74A

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A man whirls a 0.20-kg piece of lead attached to the end of a string of length 0.500 m in a circular path and in a vertical plane. If the man maintains a constant speed of 4.00 m/s, what is the tension in the string when the lead is (a) at the top of the circular path? (b) at the bottom of the circular path? (Sec Section 7.4.)
A 30.O-g ball at the end of a stung is swung in a vertical circle with a radius of 25.0 m. The rotational velocity Is 200.0 cm/s. Find the tension in the string: (a) at the top of the circle, (b) at the bottom of the circle, and (c) at a distance of 12.5 cm from the center of the circle (r=12.5cm).
Modem roller coasters have vertical loops like the one shown here. The radius of curvature is smaller at the top than on the sides so that the downward centripetal acceleration at the top will be greater than the acceleration due to gravity, keeping the passengers pressed firmly into their seats. (a) What is the speed of the roller coaster at the top of the loop if the radius of curvature there is 15.0 m and the downward acceleration of the car is 1.50 g ? (b) How high above the top of the loop must the roller coaster start from rest, assuming negligible friction? (c) If it actually starts 5.00 m higher than your answer to (b), how much energy did it lose to friction? Its mass is 1.50103kg .
Modern roller coasters have vertical loops like the one shown in Figure 6.38. The radius of curvature is smaller at the top than on the sides so that the downward centripetal acceleration at the top will be greater than the acceleration due to gravity, keeping the passengers pressed firmly into their seats. What is the speed of the roller coaster at the top of the loop if the radius of curvature there is 15.0 m and the downward acceleration of the car is 1.50 g? Figure 6.38 Teardrop-shaped loops are used in the latest roller coasters so that the radius of curvature gradually decreases to a minimum at the top. This means that the centripetal acceleration builds from zero to a maximum at the top and gradually decreases again. A circular loop would cause a jolting change in acceleration at entry, a disadvantage discovered long ago in railroad curve design. With a small radius of curvature at the top, the centripetal acceleration can more easily be kept greater than g so that the passengers do not lose contact with their seats nor do they need seat belts to keep them in place.
A string under a tension of 50.0 N is used to whirl a rock in a horizontal circle of radius 2.50 m at a speed of 20.4 m/s on a fricitonless surface as shown in Figure P6.25. As the string is pulled in, the speed of the rock increases. When the string on the table is 1.00 m long and the speed of the rock is 51.0 m/s, the string breaks. What is the breaking strength, in newtons, of the string? Figure P6.25
A space station, in the form of a wheel 120 m in diameter, rotates to provide an artificial gravity of 3.00 m/s2 for persons who walk around on the inner wall of the outer rim. Find the rate of the wheels rotation in revolutions per minute that will produce this effect.
Suppose an alien civilization has a space station in circular orbit around its home planet. The stations orbital radius is twice the planets radius, (a) If an alien astronaut has weight w just before launch from the surface, will she be weightless when she reaches the station and floats inside of it? (b) If not, what will be the ratio of her weight in orbit to her weight on the planets surface?
Estimate the gravitational force between two sumo wrestlers, with masses 220 kg and 240 kg, when they are embraced and their centers are 1.2 m apart.
Why does banking a curve on a highway allow a vehicle to successfully negotiate the turn at a higher speed?
The following objects are moving in uniform circular motion. Draw a free-body diagram for each object and identify the force responsible for the centripetal acceleration. Object 1. A person riding on the barrel-of-fun ride (Fig. 6.27, top) Object 2. The lead object in the laboratory set-up (Fig. 6.27, center) Object 3. A jogger running on a circular track (Fig. 6.27, bottom)
A number of amusement parks have rides that make loops like the one shown in Figure 6.33. For safety, the cars are attached to the rails in such a way cannot fall off. If the car goes over the top at just the right speed, gravity alone will supply the centripetal force. What other force acts and what is its direction if: (a) The car goes over the top at faster than this speed? (b) The car goes this speed? Figure 6.33 Amusement rides with a vertical loop are an example of a form of curved motion.
Railroad tracks follow a circular curve of radius 500.0 m and are banked at an angle of 5.0 . For trains of what speed are these tracks designed?

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