The acceleration of a ball as it rolls down a ramp is 3 m/s2 . It starts from rest. (a) What is the ball's speed after 4 seconds? (b) How far does the ball travel during the 4 seconds?
12 m/s, 24 m
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Astronomers know what the solar interior is like by
A. constructing a miniature Sun in the laboratory and extrapolating the results to the real Sun. B. using locally tested physics combined with observations to build a mathematical model of what the Sun should be like in its interior. C. observing the interior directly. By using the appropriate filters, it is possible to reduce the bright glow of the Sun and to peer directly at the Sun's interior. D. sending probes directly into the Sun and sending back the information.
A parallel-plate capacitor stores charge Q. The capacitor is then disconnected from its voltage source, and the space between the plates is filled with a dielectric of constant ? = 2 . What is the relationship between the stored energies of the capacitor, where PEi is the initial stored energy, and PEf is the stored energy after the dielectric is inserted?
a. PEf = 0.25PEi b. PEf = 0.5PEi c. PEf = PEi d. PEf = 2PEi
The electrical force between any two charged objects is
A. always balanced by the action-reaction forces. B. dependent on the sign of the charge on each object. C. always attractive. D. always repulsive.
The Big Bang is regarded as the expansion of
A) space. B) energy. C) time. D) matter.