A helicopter reises from rest on the ground vertically upwards wi… - Vidyadip

MCQ

A helicopter reises from rest on the ground vertically upwards with a constant acceleration $g.$ A food packet is dropped from the helicopter when it is a height $h$. The time taken by the packet to reach the ground is close to $[ g$ is the acceleration due to gravity]

A
$t =\sqrt{\frac{2 h }{3 g }}$
B
$t=1.8 \sqrt{\frac{h}{g}}$
✓
$t=3.4 \sqrt{\left(\frac{h}{g}\right)}$
D
$t=\frac{2}{3} \sqrt{\left(\frac{h}{g}\right)}$

✓

Answer

Correct option: C.

$t=3.4 \sqrt{\left(\frac{h}{g}\right)}$

c
$t_{0}=\sqrt{\frac{2 h}{g}}$

$\Rightarrow \quad u=\sqrt{\frac{2 h}{g}} \times g=\sqrt{2 g h}$

$\therefore \quad t_{1}=$time to reach top $=\frac{u}{g}=\sqrt{\frac{2 h}{g}}$

$\therefore \quad H=h+h^{\prime}=2 h$

$t_{2}=$ time of fall $=\sqrt{\frac{2 \times(2 h)}{g}}$

$\quad=2 \sqrt{\frac{h}{g}}$

Total time $=t_{1}+t_{2}$

$\quad=(2+\sqrt{2}) \sqrt{\frac{h}{g}}$

$\quad=3.4 \sqrt{\frac{h}{g}}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "SECTION - A [PHYSICS MCQ]" from STD 11 - 2. motion in straight line→STD 11 - 2. motion in straight line — all question types→JEE STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

An ideal gas is enclosed in a container of volume $V$ at a pressure $P$. It is being pumped out of the container by using a pump with stroke volume $v$. What is final pressure in container after $n$-stroke of the pump? (assume temperature remains same)

The escape velocity of an object on a planet whose $g$ value is $9$ times on earth and whose radius is $4$ times that of earth in $km/s$ is

The activity of a radioactive sample is $1.6\, curie$ and its half-life is $2.5 \,days$. Its activity after $10\, days$ will be .......... $curie$

Light of frequency $4v_0$ is incident on the metal of the threshold frequency $v_0$. The maximum kinetic energy of the emitted photoelectrons is

When an unpolarized light of intensity, $I_0$ is incident on a polarizing sheet, the intensity of light which does not get transmitted is

Aboat having a speed of $5\,\, km/hr$. in still water, crosses a river of width $1\,\, km$ along the shortest possible path in $15 \,\,minutes$. The speed of the river in $Km/hr.$

Two plane mirrors are parallel to each other and an object $O$ is placed between them. Then the distance of the first three images from the mirror $M_2$ will be (in $cm$)

A nuclear bomb exploded $200 \,km$ above the surface of moon. The sound of explosion on the moon

A block is lying on an inclined plane which makes $60^°$ with the horizontal. If coefficient of friction between block and plane is $0.25$ and $g = 10\,m/{s^2}$, then acceleration of the block when it moves along the plane will be ........ $m/s^2$

The period of oscillation of a simple pendulum is given by $T = 2\pi \sqrt {\frac{l}{g}} $ where $l$ is about $100 \,cm$ and is known to have $1\,mm$ accuracy. The period is about $2\,s$. The time of $100$ oscillations is measured by a stop watch of least count $0.1\, s$. The percentage error in $g$ is ......... $\%$