Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice power work and power work, energy and power physics energy and its forms

An engine of ine metric ton is going up an inclined plane, 1 in 2 at the rate of 36 kmph. If the coefficient of friction is $1/ \sqrt{3}$, the power of engine is 

  1. 9.8W

  2. 98W

  3. 980W

  4. 98kW
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Force required = mg * sin(theta) + mu * mg * cos(theta). Slope 1 in 2 means sin(theta) = 0.5, cos(theta) = sqrt(3)/2. Force = 1000 * 9.8 * (0.5 + (1/sqrt(3)) * (sqrt(3)/2)) = 1000 * 9.8 * (0.5 + 0.5) = 9800 N. Velocity = 36 kmph = 10 m/s. Power = F * v = 9800 * 10 = 98000 W = 98 kW.

Multiple choice power work and power work, energy and power physics energy and its forms

A train of mass $6 \times 10^2$ metric tones is pulled by a locomotive. The speed of the train will be $36 \,kmhr^{}-1$. The locomotive pulls the train on the train on the level track, whose mass is $125$ metric tones. The force of friction acts on the locomotive and the train is $1 \times 10^1$ newton per metric tonne. Calculate the power of the locomotive.

  1. 72500

  2. 6000

  3. 5000

  4. 4000
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$m = 600$
$m\ell = 125$
$m \,net = 725$
$f = \dfrac{10}{tan}$
$t _{net} = 10 \times 125$

$V = 36 \,km/h = 36 \times \dfrac{5}{18} m/s$

$P = t _{net} \times V = 72500 \,W$

Multiple choice power work and power work, energy and power physics energy and its forms

The power of water pump is The power of water pump is  $4kW.$  If  $\left( g=10{ m }{ { s }^{ -2 } } \right) ,$  the amount of water it can raise in $1$ minute to a height of $20 m$  is then

  1. $100$ litre
  2. $1000$ litre
  3. $1200$ litre
  4. $2000$ litre
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given that,

Power, $P=4\,kW=4000\,W$

Height, $h=20\,m$

Time, $t=60\,\sec $

$ power=\dfrac{work}{time} $

$ 4000=\dfrac{mgh}{t} $

$ 4000=\dfrac{m\times 10\times 20}{60} $

$ m=1200\,Kg $

The pump can raise 1200 litre in one minute

Multiple choice power work and power work, energy and power physics energy and its forms

An object of mass accelerates uniformly from rest to a speed $v _f$ in time $t _f$ Then the instantaneous power delivered to the object,as a function of time $t$ is -

  1. $mt\left(\dfrac{{v _f}^2}{t _f}\right)$
  2. $mt\dfrac{v _f}{t _f}$
  3. $\dfrac{1}{2}mt^2\left(\dfrac{v _f}{t _f}\right)^2$
  4. $\dfrac{1}{2}mt^2\left(\dfrac{v _f}{t _f}\right)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice power work and power work, energy and power physics energy and its forms

A force applied by the engine of a train of mass 2.05 x $10^{6} kg$ changes its velocity from 5 $ms^{-1}$ to 25  $ms^{-1}$ in 5 minutes. The power of the engine is then

  1. 1.025 MW

  2. 2.05 MW

  3. 5 MW

  4. 6 MW
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given that,

Mass of train, $m=2.05\times {{10}^{6}}\,Kg$

Time, $t=5\,\min utes=300\,s$

$ v=25\,m/s $

$ u=5\,m/s $

Acceleration,

$ a=\dfrac{v-u}{t} $

$ a=\dfrac{25-5}{300} $

$ a=\dfrac{2}{30}=\dfrac{1}{15}\,m/{{s}^{2}} $

Using equation of motion,

$ {{v}^{2}}-{{u}^{2}}=2as $

$ {{(25)}^{2}}-{{(5)}^{2}}=2\times \dfrac{1}{15}\times s $

$ s=4500\,m $

Power,

$ P=\dfrac{work\,\,done}{time} $

$ P=\dfrac{F\times d}{t} $

$ P=\dfrac{m\times a\times s}{t} $

$ P=\dfrac{2.05\times {{10}^{6}}\times 1\times 4500}{15\times 300} $

$ P=2.05\times {{10}^{6}}\,W $

$ P=2.05\,MW $

Multiple choice power work and power work, energy and power physics energy and its forms

A motor lifts $100 kg$ of water in $2 min$ from a well of $60m$ depth then the electric power of the motor is$(Taken g=10 m/s^2)$

  1. $1000 W$
  2. $750 W$
  3. $1200 W$
  4. $500W$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A motor lifts $=100kg$ of water

Time $=2min=2\times60=120s$
Depth$=60m$ depth then,
electric power of the motor$=?$
Taking $=10m/s^2$
$P=Power=\cfrac{mgh}{t}\ \quad=\cfrac{100\times10\times60}{120}\ \quad=500W$

Multiple choice power work and power work, energy and power physics energy and its forms

A force $'F'$ accelerates a block of mass $'m'$ along a straight line to velocity $'v'$ from rest and displace it through a distance $'s'$. What is the average power developed?

  1. $\dfrac {v^{2}}{2F}$
  2. $Fv$
  3. $\dfrac {mv^{2}}{2s}$
  4. $\dfrac {Fv}{2}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For constant acceleration starting from rest, v_avg = v / 2. Average Power = F * v_avg = F * (v / 2).

Multiple choice power work and power work, energy and power physics energy and its forms

A pump ejects $12000kg$ of water at speed of $4m/s$ in $40$ second. Find the average rate at which the pump is working

  1. $0.24KW$
  2. $2.4KW$
  3. $24KW$
  4. $24W$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Force = change in momentum / time = (m * v) / t = (12000 * 4) / 40 = 1200 N. Power = Force * velocity = 1200 * 4 = 4800 W = 4.8 kW. The provided answer 2.4 kW suggests the calculation might be (1/2) * m * v^2 / t = (0.5 * 12000 * 16) / 40 = 2400 W = 2.4 kW, which is the rate of kinetic energy delivery.