During the T-Tauri phase of a protostar, it
A) begins a period of reduced activity.
B) expands dramatically.
C) may develop very strong winds.
D) lies on the main sequence.
E) changes its spin direction.
C
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Find the radius of a star image formed on the retina of the eye if the aperture diameter (the pupil) at night is 0.70 cm and the length of the eye is 3.2 cm. Assume the wavelength of starlight in the eye is 500 nm. (1 nm = 10?9 m)
a. 2.8 × 10^?4 m b. 5.6 × 10^?4 m c. 3.1 × 10^?5 m d. 2.8 × 10^?6 m e. 3.2 × 10^?4 m
A charged particle (q = -8.0 mC), which moves in a region where the only force acting on the particle is an electric force, is released from rest at point A. At point B the kinetic energy of the particle is equal to 4.8 J. What is the electric potential difference VB - VA?
a. -0.60 kV b. +0.60 kV c. +0.80 kV d. -0.80 kV e. +0.48 kV
If you pitch a baseball with twice the kinetic energy you gave it in a previous pitch, the magnitude of its momentum is
A) 4 times as much. B) 2 times as much. C) doubled. D) times as much. E) the same.
To turn 50 grams of boiling water to steam requires
A) 50 calories. B) 500 calories C) 540 calories. D) more than 540 calories. E) none of the above