The magnetic force on a charged particle moving at a constant speed in a uniform magnetic field will be halved when the angle between the velocity of the particle and the direction of the magnetic field changes from 25.0 to
a. 50.0.
c. 57.7.
b. 12.5.
d. 12.2.
[Ques. 2] How much air must be pushed downward at 60.0 m/s to keep an 800-kg helicopter aloft?
a. 131 kg/s
c. 294 kg/s
b. 196 kg/s
d. 392 kg/s
[Ques. 3] The magnetic force on a charged particle moving at a constant speed in a uniform magnetic field will be doubled when the angle between the velocity of the particle and the direction of the magnetic field changes from 25.0 to
a. 57.7.
c. 12.2.
b. 12.5.
d. 50.0.
[Ques. 4] The Garfield Thomas water tunnel at Pennsylvania State University has a circular cross-section that constricts from a diameter of 3.6 m to the test section, which is 1.2 m in diameter. If the speed of flow is 2.0 m/s in the large-diameter pipe, determine the speed of flow in the test section.
a. 9.0 m/s
c. 27 m/s
b. 18 m/s
d. 1.0 m/s
[Ques. 5] An electron is moving at a speed of 12 106 m/s at an angle of 30 with respect to a uniform magnetic field of 8.0 104 T. What is the radius of the resulting helical path? (me = 9.11 1031 kg, qe = 1.6 1019 C)
a. 2.1 cm
c. 4.3 cm
b. 3.7 cm
d. 8.5 cm
[Ques. 6] A fountain sends water to a height of 50 m. What must be the pressurization (above atmospheric) of the underground water system? (1 atm = 105 N/m2)
a. 1 atm
c. 7.2 atm
b. 4.9 atm
d. 9.8 atm
[Ques. 7] A proton with initial kinetic energy E is moving in circular motion in a uniform magnetic field. When it has completed one fourth of a revolution, what is its kinetic energy?
a. 1.4 E
c. E
b. 0.71 E
d. The value is not given.
[Ques. 8] Water pressurized to 4 105 Pa is flowing at 5.0 m/s in a pipe which contracts to 1/3 of its former area. What are the pressure and speed of the water after the contraction? (density of water = 1 103 kg/m3)
a. 2 105 Pa, 15 m/s
c. 3 105 Pa, 15 m/s
b. 3 105 Pa, 10 m/s
d. 4 105 Pa, 1.5 m/s
[Ques. 9] At the Fermilab accelerator in Weston, Illinois, singly-charged ions with momentum 3.2 10-16 kgm/s are held in a circular orbit of radius 1 km by an upward magnetic field. What B-field must be used to maintain the ions in this orbit? (qion = 1.6 10-19 C)
a. 4 T
c. 1 T
b. 2 T
d. 3 T
[Ques. 10] Water comes down the spillway of a dam from an initial vertical height of 100 m. What is the highest possible speed of the water at the end of the spillway?
a. 15 m/s
c. 58 m/s
b. 44 m/s
d. 1370 m/s
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