A 2.0-kg mass swings at the end of a light string (length = 3.0 m). Its speed at the lowest point on its circular path is 6.0 m/s. What is its kinetic energy at an instant when the string makes an angle of 50° with the vertical?
a. 21 J
b. 15 J
c. 28 J
d. 36 J
e. 23 J
B
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When visible light is incident upon clear glass, atoms in the glass
A) are forced into vibration. B) resonate. C) convert the light energy into internal energy.
A force of 120 N is applied to an object whose mass is 30 kg. The object's acceleration is
A) 3600 m/s2. B) 150 m/s2. C) 4.0 m/s2 D) 2.0 m/s2. E) 0.25 m/s2.
The event in the life of a star that begins its expansion into a giant is
A) the core reaches a temperature of ten million degrees B) as much as 90% of the star explodes violently C) almost all the hydrogen in its core that was hot enough for fusion has been turned into helium D) the star's internal structure reaches equilibrium for the first time in its life E) it reaches the stage that astronomers call the zero-age main sequence
If a calculated quantity has units of T ? m/A, that quantity could be
A) an electric field. B) an electric potential. C) ?0. D) a magnetic field. E) a magnetic torque.