A rock is thrown from ground level at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the magnitude of the velocity of the rock right before it hits the ground?
A) It is equal to its initial vertical velocity.
B) It is equal to its initial horizontal velocity.
C) It is equal to the magnitude of its initial velocity.
D) 0
E) Cannot be determined without additional information.
C
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The Doppler method seeks to detect planets by
A) precisely measuring distances to stars. B) directly detecting the light of planets orbiting stars. C) measuring small changes in the positions of stars on the sky. D) precisely measuring the velocities of stars moving toward and away from us. E) measuring small changes in the apparent brightness of stars.
Suppose that the Sun—Earth distance were 10 AU instead of 1 AU. Then the energy of sunlight received per square meter on Earth each second would be ________ it is today.
A) 10 times as great as B) about the same as C) 1/100 as much as D) 100 times as great as E) 1/10 as much as
It is likely that the density of the universe is made up mostly of
A. hydrogen B. electromagnetic radiation C. dark energy D. cold dark matter
Most surface ocean currents are due to
A) melting polar glaciers. B) river flow into the ocean. C) winds. D) density differences in the vertical profile of the ocean.