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# Circular Motion

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1. Centrifuges are commonly used in biological laboratories for the isolation and maintenance of cell preparations. For cell separation, assume centrifugation conditions that are 1.00 x 103 rpm using an 8.31-cm-radius rotor. What is the radial acceleration of material in the centrifuge under these conditions? Express your answer as a multiple of g. Do not enter unit.

2. At 1.00 x 103 rpm (and with a 8.31-cm rotor) what is the net force on a red blood cell whose mass is 9.12 x 10-14 kg?

3. What is the net force on a virus particle of mass 4.95 x 10-21 kg under the same conditions?

4. To pellet out virus particles and even to separate large molecules such as proteins, super-high-speed centrifuges called ultracentrifuges are used in which the rotor spins in a vacuum to reduce heating due to friction. What is the radial acceleration inside an ultracentrifuge at 75500 rpm with an 8.31-cm rotor? Express your answer as a multiple of g. Do not enter unit.

https://brainmass.com/physics/acceleration/circular-motion-273864

#### Solution Summary

This solution is comprised of detailed step-by-step calculations and analysis of the given problems related to Physics and provides students with a clear perspective of the underlying concepts.

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## Four problems about tension and circular motion

(See attached file for full problem description)

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1. In a tug-of-war, each man on a 5-man team pulls with an average force of 500 N. What is the tension in the center of the rope?

A zero newtons
B 100 N
C 500 N
D 2500 N
E 5000 N

2. A ball moves with a constant speed of 4 m/s around a circle of radius 0.25 m. What is the period of the motion?

A 0.1 s
B 0.4 s
C 0.7 s
D 1 s
E 2 s

3. A race car is traveling at constant speed around a circular track. What happens to the centripetal acceleration of the car if the speed is doubled?

A It remains the same.
B It increases by a factor of 2.
C It increases by a factor of 4.
D It is decreased by a factor of one-half.
E It is decreased by a factor of one-fourth.

4. A car enters a horizontal, curved roadbed of radius 50 m. The coefficient of static friction between the tires and the roadbed is 0.20. What is the maximum speed with which the car can safely negotiate the unbanked curve?

A 5 m/s
B 10 m/s
C 20 m/s
D 40 m/s
E 100 m/s
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(See attached file for full problem description)

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