Speed, Time and Distance - Quant/Math -
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Question 4 the day: September 23, 2002
The question for the day is from the topic of Speed, Time and Distance.

When an object is dropped, the number of feet N that it falls is given by the formula N = ½gt² where t is the time in seconds from the time it was dropped and g is 32.2. If it takes 5 seconds for the object to reach the ground, how many feet does it fall during the last 2 seconds?

(1)

64.4

(2)

96.6

(3)

161.0

(4)

257.6

Solution:

In 5 seconds it travels
½ * 32.2 * 5² = 16.1 * 25 = 402.5
In first 3 seconds it travels
½ * 32.2 * 3² = 16.1 * 9 = 144.9
Hence in the last 2 seconds it traveled 402.5 - 144.9 = 257.6