The energy radiated by a star, such as the sun, results chiefly from
A) beta decay.
B) alpha decay.
C) fission reactions.
D) fusion reactions.
E) radioactivity.
D
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A concave mirror has a focal length of 20 cm. What is the position (in cm) of the resulting image if the image is inverted and four times smaller than the object?
a. 15 b. 25 c. 50 d. 100 e. -15
In a thermodynamic process, the internal energy of a system in a container with adiabatic walls decreases by 800 J. Which statement is correct?
a. The system lost 800 J by heat transfer to its surroundings. b. The system gained 800 J by heat transfer from its surroundings. c. The system performed 800 J of work on its surroundings. d. The surroundings performed 800 J of work on the system. e. The 800 J of work done by the system was equal to the 800 J of heat transferred to the system from its surroundings.
A pendulum consists of a 2.0-kg block hanging on a 1.5-m length string. A 10-g bullet moving with a horizontal velocity of 900 m/s strikes, passes through, and emerges from the block (initially at rest) with a horizontal velocity of 300 m/s. To what maximum height above its initial position will the block swing?
a. 32 cm b. 38 cm c. 46 cm d. 27 cm e. 9 cm
A 20.0-N box rests on a 50.0-N box on a perfectly smooth horizontal floor. When a horizontal 15.0-N pull to the right is exerted on the lower box (see figure), both boxes move together
Find the magnitude and direction of the net external force on the upper box. What will be an ideal response?