The graph above shows 4 models for how the average distance between galaxies could change with time, from the past (left) to now (middle) to the future (right-hand side). The graph also shows real data, based on white dwarf supernovae. Which model predicts that galaxies had the largest separations in the past?
A) accelerating
B) coasting
C) critical
D) recollapsing
A) accelerating
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Which of the following describes a major danger of interstellar travel at near-light speed?
A) Atoms and ions in interstellar space will hit a fast-moving spacecraft like a flood of dangerous cosmic rays. B) Any interstellar journey will take much longer than the lives of the crew members. C) Time dilation will slow the heart beats of the crew to a dangerously low rate. D) Asteroid fields floating in interstellar space will present a navigational challenge.
The net work done in accelerating a propeller from rest to an angular velocity of 200 rad/s is 3000 J. What is the rotational inertia of the propeller?
What will be an ideal response?
A cheetah can run at approximately 100 km/h and a gazelle at 80.0 km/h. If both animals are running at full speed, with the gazelle 50.0 m ahead, how long before the cheetah catches its prey?
a. 9.0 s b. 14 s c. 18 s d. 4.5 s e. 21 s
A velocity selector uses a fixed electric field of magnitude E and the magnetic field is varied to select particles of various energies. If a magnetic field of magnitude B is used to select a particle of a certain energy and mass, what magnitude of magnetic field is needed to select a particle of equal mass but twice the energy?
a. 0.50 B b. 1.4 B c. 2.0 B d. 0.71 B e. 1.7 B