Aptitude Discussion

Q. |
When an object is dropped, the number of feet N that it falls is given by the formula (N=dfrac{1}{2}gt^2) 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? |

✖ A. |
64.4 |

✖ B. |
96.6 |

✖ C. |
161.0 |

✔ D. |
257.6 |

**Solution:**

Option(**D**) is correct

In 5 seconds it travels

\(=\left(\dfrac{1}{2}\right)\times 32.2\times 52\)

\(=16.1\times 25\)

\(=402.5\)

In first 3 seconds it travels

\(=\left(\dfrac{1}{2}\right)\times 32.2\times 32\)

\(=16.1Ã—9\)

\(=144.9\)

Hence in the last 2 seconds it travelled $402.5−144.9$= **257.6**