A proton moving at 6.0 × 10^4 m/s is projected at an angle of 30° above a horizontal plane. If an electric field of 400 N/C is acting down, how long does it take the proton to return to the horizontal plane? (Hint: Ignore gravity. mproton = 1.67 × 10^-27 kg, qproton = 1.6 × 10^-19 C)
a. 7.8 × 10^-6 s
c. 7.8 × 10^-7 s
b. 1.6 × 10^-6 s
d. 3.9 × 10^-6 s
B
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Answer the following statement(s) true (T) or false (F)
1. The frequencies of the normal modes of a string that is free at both ends are the same as those of a string that is fixed at both ends
A neutral atom loses one of its electrons. It is then
A) a negative ion. B) either a negative or positive ion, depending on which electron was lost. C) a positive ion. D) ashamed of itself. E) a neutral ion.
A 385-g tile hangs from one end of a string that goes over a pulley with a moment of inertia of 0.0125kg.m2 and a radius of 15.0 cm. A mass of 710 g hangs from the other end of the string. When the tiles are released, the larger one accelerates downward while the lighter one accelerates upward. The pulley has no friction in its axle and turns without the string slipping. What is the tension in the string on the side of the 710-g tile?
A) 9.77 N B) 5.59 N C) 3.68 N D) 6.87 N E) 4.41 N
A balloon of negligible mass is filled with 300 m3 of helium. How big a payload can the balloon lift? (The density of air is 1.29 kg/m3; the density of helium is 0.18 kg/m3.)
a. 150 kg c. 333 kg b. 300 kg d. 444 kg