A figure skater is spinning with her arms extended. She now pulls her arms close to her body. What happens?
A. The net external torque on her increases
B. Her rotational inertia decreases
C. Her angular acceleration decreases
D. Her lever arm gets shorter
Answer: B
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Select the best filter for a cobalt x-ray tube that will reduce the intensity of the K? line and transmit the cobalt K? line.
(a) What are the wavelength of the cobalt K? and K? line? (b) What is your selected filter material? (c) What is the wavelength of the K absorption edge of your selected filter material?
A boat loaded with scrap iron floats in a swimming pool. When the iron is thrown overboard, the pool level will
A) rise. B) fall. C) remain unchanged.
A ball is thrown upward with a speed and direction such that it reaches a maximum height of 18.0 m above the point it was released. At its maximum height it has a speed of 20.0 m/s. With what speed was the ball released?
A) 27.4 m/s B) 24.3 m/s C) 35.1 m/s D) 31.3 m/s E) 39.0 m/s
Suppose a beam of electrons is incident on a collection of hydrogen atoms, all of which are in the lowest energy state (n = 1). What is the minimum energy the electrons can have if they are to excite the hydrogen atoms into the n = 2 state?