A pebble is dropped from rest from the top of a tall cliff and falls 4.9 m after 1.0 s has elapsed. How much farther does it drop in the next 2.0 s?
(a) 9.8 m
(b) 19.6 m
(c) 39 m
(d) 44 m
(e) none of the above.
Hence, option (c) 39 m is correct.
The magnitude of an object's rate of change of position with time, or the magnitude of change of position per unit of time, is its speed. It is thus a scalar quantity.
The distance travelled in 1s is m
Let be the distance travelled in the next 2s
Total distance travelled in
From the equation of motion,
role="math" localid="1663684119423"Therefore, at approximately 39 m the pebble dropped in the next 2.0 s.
A juggler throws a bowling pin straight up in the air. After the pin leaves his hand and while it is in the air, which statement is true?
(a) The velocity of the pin is always in the same direction as its acceleration.
(b) The velocity of the pin is never in the same direction as its acceleration.
(c) The acceleration of the pin is zero.
(d) The velocity of the pin is opposite its acceleration on the way up.
(e) The velocity of the pin is in the same direction as its acceleration on the way up.
A skateboarder starts from rest and moves down a hill with constant acceleration in a straight line, traveling for 6 s. In a second trial, he starts from rest and moves along the same straight line with the same acceleration for only 2 s. How does his displacement from his starting point in this second trial compare with that from the first trial? (a) one-third as large (b) three times larger (c) one-ninth as large (d) nine times larger (e) times as large.
A man drops a rock into a well. (a) The man hears the sound of the splash 2.40 s after he releases the rock from rest. The speed of sound in air (at the ambient temperature) is 336 m/s. How far below the top of the well is the surface of the water? (b) What If? If the travel time for the sound is ignored, what percentage error is introduced when the depth of the well is calculated?
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