Question

A helicopter is ascending vertically with a speed of 8 m/s. At a height of 120m above the Earth, a packet is dropped from a window. How much time does it take for the packet to reach the ground is n seconds, then value of n is

Answer 1

Given: A helicopter is ascending vertically with a speed of 8 m/s and the correct height is 12 m instead of 120 m.

To find: How much time does it take for the packet to reach the ground?

Solution:

• We have given that A helicopter is ascending vertically with a speed of 8 m/s, so the initial velocity is 8 m/s.

• At a height of 12 m above the earth a packet is dropped from a window, so the height is 12 m.

• Let the time taken be n (as given in the question)

• Lets consider a = -g = -10 m/s² (as coming down so negative)

• Now we have the formula:

           s = un + 1/2 x (-a)n²

          -12 = 8n - 1/2 x 10n²

          -12 = 8n - 5n²

           5t² - 8n - 12 = 0

           n = 2.53 seconds

Answer:

              So the time taken n is 2.53 seconds.