Briefly describe how a star forms.
What will be an ideal response?
In cold, dense molecular clouds, gravity brings material together. As gas moves inward, it converts gravitational potential energy to thermal energy and warms up. Once the cloud becomes so dense that the thermal radiation cannot escape, the temperature rises rapidly, nuclear fusion begins, and the dense core becomes a protostar. As the cloud has collapsed from a large size to a small size, it must spin very fast to conserve angular momentum. This results in the formation of a protostellar disk around the protostar. Planets may form in this disk as the star continues to grow. Eventually stellar winds and jets clear away the surrounding gas and a newly formed star emerges.
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Current: A total of 2.0 × 1013 electrons pass a given point in a wire in 15 s. What is the current in the wire? (e = 1.60 × 10-19 C)
A. 1.3 mA B. 1.3 A C. 0.21 ?A D. 3.2 ?A
Molly measures a Hubble constant of 20 km/sec/million light-years. Sam measures a Hubble constant of 25 km/sec/million light-years. All other assumptions being the same, which person would estimate a LARGER age to the universe?
A) Sam B) Molly C) They both would measure the same age.
In Newton's first law, the ________ of a body causes it to resist changes in its motion
Fill in the blank(s) with correct word
An electron (charge ?1.6 × 10^?19 C) moves on a path perpendicular to the direction of a uniform electric field of strength 2.0 N/C. How much work is done on the electron as it moves 14.0 cm?
a. 5.6E–19 J b. ?2.8E–19 J c. 1.6E–19 J d. 3.9E–18 J e. zero