Question

A body falling freely under gravity from rest from a certain height reaches the ground in \(5\) seconds. The distance travelled by the body in the last two seconds of its motion is:

• A. \(98 \, {m}\)
• B. \(44.1 \, {m}\)
• C. \(58.8 \, {m}\)
• D. \(78.4 \, {m}\)

Hint:

For objects in free fall, remember the distance increases quadratically with time due to the constant acceleration of gravity.

Answer 1

The Correct Option is D

Step 1: Determine the total distance fallen in 5 seconds. 
Using the formula for distance travelled under gravity: \[ s = \frac{1}{2}gt^2 = \frac{1}{2}(9.8 \, {m/s}^2)(5^2) = 122.5 \, {m} \] Step 2: Determine the distance fallen in the first 3 seconds. \[ s_1 = \frac{1}{2}(9.8 \, {m/s}^2)(3^2) = 44.1 \, {m} \] Step 3: Calculate the distance in the last two seconds. \[ s_2 = s - s_1 = 122.5 \, {m} - 44.1 \, {m} = 78.4 \, {m} \]