Question

an object falls freely from rest for 5 seconds. Find the distance travelled in the last 2 seconds. (g=9.8m/s square)

Answer 1

Question#19337

an object falls freely from rest for 5 seconds. Find the distance travelled in the last 2 seconds. (g=9.8m/s square)

Solution:

The distance is:

$H = H_0 - H_1$, were $H_0$ – full distance travelled from 5 sec, $H_1$ – distance travelled at first 3 sec

$H = gt_0^2 / 2 - gt_1^2 / 2$, were $t_0 = 5$ sec., $t_1 = 3$ sec,

$H = 9.8 * 5^2 / 2 - 9.8 * 3^2 / 2 = 78.4 \, \text{m}$

Answer: 78.4 m.