A method for identifying a black hole is to
A) search for radio waves from the accretion disk.
B) locate a visible star that disappears when the black hole passes in front of it.
C) search for their pulsar signal.
D) look for voids in the star fields.
E) look for its effects on a nearby companion.
E
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A jet has an angular length of 10 seconds of arc and flows from a star at a distance of 2,000 pc. How far does this jet extend away from the star?
a. 20,000 pc b. 20,000 AU c. 20, 000 ly d. 20,000 miles e. 20,000 km
Referring to how many kilograms of ice can a 3-ton refrigeration unit produce in a 24-hour period? The heat of fusion of water is 330 kJ/kg.
GIVEN - A three-ton refrigeration unit - Heat of fusion of ice is 330 kJ/kg FIND (a) Kilograms of ice produced by the unit per 24 hour period (b) The refrigeration unit capacity is the net value, i.e., it includes heat losses ASSUMPTIONS (a) Water is cooled to just above the freezing point before entering the unit
Which body continually emits electromagnetic waves?
A) the Sun B) the Earth C) you and your classmates D) all of the above E) none of the above
Omar throws a rock down with speed 2.0 m/s from the top of a tower. The rock hits the ground after 2.0 s. What is the height of the tower? (air resistance is negligible)
a. 20 m c. 44 m b. 24 m d. 63 m