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 that,

Initial speed of the helicopter, u = 8 m/s

At a height of 120 m  above the Earth, a packet is  dropped from a window, h = 120 m.

To find,

We need to find the time taken  for the packet to reach the  ground is n seconds.

Solution,

Using second equation of motion to find it :

$h=ut+\dfrac{1}{2}at^2$

a = -g

$h=ut-\dfrac{1}{2}gt^2$

$120=8t-\dfrac{1}{2}\times 10t^2\\\\120=8t-5t^2\\\\5t^2-8t-12=0$

t = 2.54 seconds

So, time taken  for the packet to reach the  ground is 2.54 seconds.

Learn more,

Kinematics

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