Tag: physics

Questions Related to physics

How much is the hydrostatic pressure exerted by water at the bottom of a beaker? Take the depth of water as 45 cm. (density of water $10^3 kg m^{-3})$.

physics forces and matter pressure in fluids pressure in liquids introduction to pressure

  1. 2410 Pa

  2. 3410 Pa

  3. 4410 Pa

  4. 5410 Pa

Show answer
Correct Option: C
Explanation:

$Height=45 cm=0.45 m$,
$gravity=9.8 ms^{-2}$
$Density=1000 kg m^{-3}$
$Pressure=hdg$
$=0.45\times 9.8\times 1000Pa=4410 Pa$.

The pressure in a water pipe on the second floor of a building is 60,000 Pa, and on the third floor it is 30,000 Pa. Find the height of the second floor. (Density of water $=1000 kg m^{-3}, g=10 m s^{-2})$.

physics forces and matter pressure in fluids pressure in liquids introduction to pressure

  1. 3 m

  2. 4 m

  3. 5 m

  4. 6 m

Show answer
Correct Option: A
Explanation:

Second floor :
$P _1=60,000 Pa, g=10 ms^{-2}$
$P _1=h _1dg$


$60,000=h _1\times 1000\times 10$

$h _1=\dfrac {60,000}{1000\times 10}=6 m$

[where $h _1=$ height of water tank above second floor]

Third floor :
$P _2=30,000 Pa, g=10 m s^{-2}$,


$\therefore 30,000=h _2\times 1000\times 19$

$\Rightarrow h _2=\dfrac {30000}{1000\times 10}=3 m$

[where $h _2=$ height of water tank above first floor]

$\therefore $ height of the second floor
$=h _1-h _2=6m-3m=3m$

The pressure in water pipe at the ground floor of a building is 120000 Pa, where as the pressure on a third floor is 30000 Pa. What is the height of third floor?
[Take $g=10 m s^{-2}$, density of water $=1000 kg m^{-3}]$.

physics forces and matter pressure in fluids pressure in liquids introduction to pressure

  1. 9 m

  2. 10 m

  3. 11 m

  4. 12 m

Show answer
Correct Option: A
Explanation:

Difference in pressure of water at ground floor and third floor
$=(120000-300000)=900000 Pa$
Density of water $=1000 kg m^{-3}$
Let 'h' be the height third floor.
$P=hdg$
$h=\dfrac {p}{dg}=\dfrac {90000}{1000\times 10}=9m$.

The pressure of water on the ground floor is 50000 Pa and at the first floor is 20000 Pa. Find the height of the first floor. Take density of water is $10^3 kg m^{-3}$ and $g=10 ms^{-2}$

physics forces and matter pressure in fluids pressure in liquids introduction to pressure

  1. 2 m

  2. 3 m

  3. 4 m

  4. 5 m

Show answer
Correct Option: B
Explanation:

Pressure on the ground floor $=$ Pressure on the first floor + hdg
$\Rightarrow 50000=20000+hdg$
$\Rightarrow 50000=20000+h\times 10^3\times 10$
$\Rightarrow h\times 10^4=50000-20000$
$\Rightarrow h=\frac {30000}{10000}m$
$\Rightarrow height=3 m.$

Calculate the pressure exerted by 0.8 m vertical length of alcohol of density $0.8 g cm^{-3}$. (Acceleration due to gravity $(g)=10 m s^{-2})$.

physics forces and matter pressure in fluids pressure in liquids introduction to pressure

  1. 3200 Pa

  2. 6400 Pa

  3. 800 Pa

  4. 5000 Pa

Show answer
Correct Option: B
Explanation:

Vertical length of the alcohol column
$(h)=0.8 m$
Density of alcohol $(d)=0.8 g cm^{-3}$
$=0.8\times 1000=800 kg m^{-3}$
$[\therefore 1 g cm^{-3}=1000 kg m^{-3}]$
$Pressure = hdg$
$=0.8\times 800\times 10$
$=6400 Pa$
Therefore, pressure exerted by the alcohol column is 6400 Pa.

Calculate the pressure exerted by water at the bottom of a lake of depth 6 m. (Density of water $=1000 kg m^{-3}, g=10 ms^{-2})$.

physics forces and matter pressure in fluids pressure in liquids introduction to pressure

  1. $2\times 10^4 Pa$

  2. $4\times 10^4 Pa$

  3. $6\times 10^4 Pa$

  4. $8\times 10^4 Pa$

Show answer
Correct Option: C
Explanation:

Height $(h)=6 m$,

$density=1000 kg m^{-3}$,
$g=10 m s^{-2}, Pressure = ?$
$P=hdg$
$=6\times 1000\times 10 Pa$
$=60000 Pa$
$=6\times 10^4 Pa.$

Calculate the vertical height of a mercury column which exerts a pressure of 81600 Pa. (Density of mercury is $13.6 g cm^{-3}$ and $g=10 ms^{-2})$.

physics forces and matter pressure in fluids pressure in liquids introduction to pressure

  1. 0.2 m

  2. 0.4 m

  3. 0.6 m

  4. 0.8 m

Show answer
Correct Option: C
Explanation:

$Pressure (P)=81600 Pa$
$Density (d)=13.6 g cm^{-3}$
$=13.6\times 1000 kg m^{-3}$
$(\therefore 1 g cm^{-3}=1000 kg m^{-3})$

Acceleration due to gravity $(g)=10 ms^{-2}$
$P=hdg$
$\Rightarrow h=\dfrac {P}{dg}=\dfrac {81600}{13.6\times 1000\times 10}$
$\Rightarrow h=0.6 m$
Therefore, vertical height of mercury column is 0.6 m.

A liquid of density $12 kg m^{-3}$ exerts a pressure of 600 Pa at a point inside a liquid. What is height of liquid column above that point? $[g=10 ms^{-2}]$

physics forces and matter pressure in fluids pressure in liquids introduction to pressure

  1. 4 m

  2. 5 m

  3. 6 m

  4. 7 m

Show answer
Correct Option: B
Explanation:

$Denstiy = 12 kg m^{-3}, Pressure=600 Pa$
$Pressure=hdg$
$\Rightarrow hdg=Pressure\Rightarrow height=\dfrac {P}{dg}$
$=\dfrac {600}{12\times 10}m=5m.$

A metal cube is placed in an empty vessel. When water is filled in the vessel so that  cube is completely immersed in the water, the force on the bottom of the vessel in contact with the cube-

physics forces and matter pressure in fluids pressure in liquids introduction to pressure

  1. Will increase

  2. Will decrease

  3. Will remain the same

  4. Will become zero

Show answer
Correct Option: C

Standing liquid exerts pressure on the bottom due to its:

physics forces and matter pressure in fluids pressure in liquids introduction to pressure

  1. mass

  2. weight

  3. both mass and weight

  4. none of these

Show answer
Correct Option: C
Explanation:

Every liquid has a density and volume which implies that it has mass & all the bodies having under gravity exerts weight.