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Physics For Scientists & Engineers
Found in: Page 49

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Short Answer

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.

See the step by step solution

Step by Step Solution

Step 1: Definition of speed

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.

Step 2: Explanation for correct answer


Initial velocity v0=0

The distance travelled in 1s is Δx1=4.9 m

Let x be the distance travelled in the next 2s

Total distance travelled in 3s=4.9 m+x

From the equation of motion, Δx=vet+12at2

role="math" localid="1663684119423" 4.9 m+x=12(9.8 m/s2)(3 s)2 x=12(9.8 m/s2)(3 s)2 x=39.2 m 39 m

Therefore, at approximately 39 m the pebble dropped in the next 2.0 s.

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