A river 100 m wide flows due south at 1 m/s. A boat that goes 1 m/s relative to the water leaves the west bank. To land at a point due east of its starting point, the boat must be pointed
A) northeast.
B) east.
C) southeast.
D) nowhere–it can't be done.
Answer: D
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Suppose you have three identical lightbulbs, some wire, and a battery. You connect one lightbulb to the battery and take note of its brightness. You add a second lightbulb, connecting it in parallel with the previous lightbulbs, and again take note of the brightness. Repeat the process with the third lightbulb, connecting it in parallel with the other two. As the lightbulbs are added, the
individual currents in the lightbulbs (neglect the battery’s internal resistance) 1.increases. 2.decreases. 3.remains the same. 4.Need more information.
A helium-neon laser emits red light having a wavelength of 632.8 nm and a power of 10 mW. How many photons are emitted each second? (h = 6.63 × 10^-34 J×s, c = 3.00 × 10^8 m/s, and 1 nm = 10-9 m)
a. 4.8 × 10^17 c. 3.2 × 10^16 b. 1.6 × 10^15 d. 2.6 × 10^18
A salt will dissolve in water to form:
a. acids b. gases c. ions d. bases e. polar solvents
Solenoid: Consider an ideal solenoid of length L, N windings, and radius b (L is much longer than b). A current I is flowing through the wire windings. If the length of the solenoid becomes twice as long (to 2L), but all other quantities remained the same, the magnetic field inside the solenoid will
A. remain the same. B. become twice as strong as initially. C. become one-half as strong as initially. D. become four times as strong as initially. E. become one-fourth as strong as initially.