A girl whirls a ball on the end of a string above her head. Assume the motion of her hand to keep the ball in motion is negligible. For the ball to remain in a circular path while it rotates with a constant speed:
a. only the centripetal force shown in the figure is required.
b. in addition to the centripetal force shown in the figure, there must also be a force tangent to the motion of the ball.
c. in addition to the centripetal force shown in the figure, there must also be a centrifugal force that pulls the ball outward.
d. in addition to the centripetal force shown in the figure, there must also be a force radially inward from the string to cause circular motion.
e. the centripetal force inward and the centrifugal force outward must balance each other.
a
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When we see x-rays from an accretion disk in a binary system, we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole. Suppose we then observe each of the following phenomena in this system. Which one would rule out the possibility of a black hole?
A) intense x-ray bursts B) spectral lines from the companion star that alternately shift to shorter and longer wavelengths C) visible and ultraviolet light from the companion star D) bright x-ray emission that varies on a time scale of a few hours
What are Saturn's rings?
A) a great disk of liquid helium B) large rocky boulders moving in orbit around Saturn C) a glowing, flat magnetospheric auroral display D) a solid thin disk of material encircling Saturn E) small icy particles moving in orbit around Saturn
When work is done by a system and no heat is added, the temperature of the system
A) increases. B) decreases. C) remains unchanged.
On an alien planet, an object moving at 4.0 m/s on the horizontal ground comes to rest after traveling a distance of 10 m. If the coefficient of kinetic friction between the object and the surface is 0.20, what is the value of g on that planet?
A) 4.0 m/s2 B) 6.0 m/s2 C) 8.0 m/s2 D) 10 m/s2 E) 12 m/s2