Rotational Kinetic Energy: A solid uniform disk of diameter 3.20 m and mass 42 kg rolls without slipping to the bottom of a hill, starting from rest. If the angular speed of the disk is 4.27 rad/s at the bottom, how high did it start on the hill?
A. 3.57 m
B. 2.68 m
C. 3.14 m
D. 4.28 m
Answer: A
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A concave mirror has a focal length of 20 cm. What is the magnification if the object's distance is 100 cm?
a. 1/2 b. 1/4 c. ?2 d. 4 e. ?1/4
Two solenoids are each made of 2 000 turns of copper wire per meter. Solenoid I is 2 m long, while solenoid II is 1 m long. When equal currents are present in the two solenoids, the ratio of the magnetic field BI along the axis of solenoid I to the magnetic field BII along the axis of solenoid II, BI/BII, is
a. 1/4. b. 1/2. c. 1. d. 2 e. 4.
Are electric fields made of material particles such as atoms, and how do we know?
A) Yes, because electric fields have energy and all forms of energy are associated with material particles. B) No, because electromagnetic waves are able to cross regions of empty space containing no material particles. C) Yes, because the forces exerted by electric fields are always exerted on material particles such as atoms. D) No, because electric fields are observed to exist even within protons, and protons are not material particles. E) Yes, because everything is made of atoms.
It is generally believed that there are 7 days in a week because
a. there are 7 stars in the Big Dipper. b. it is necessary to have 52 weeks in a year. c. there are 7 visible bodies in the sky that move against the background of the fixed stars. d. it is easy to multiply by 7.