Question 3 :
The power of a crane is 6.25 kW. How much mass of coal it can lift in 1 hour from a mine of 100 m depth? The efficiency of the crane is 80% and $g = 10 \ m s^{-2}$.
Question 7 :
If the force applied is $F$ and the velocity gained is $v$, then the power developed is:
Question 9 :
A juggler throws continuously balls at the rate ofthree in each second each with a velocity of $10\ ms^{-1}$. If the mass of each ball is $0.05\ kg$ hispower is:
Question 14 :
A car of mass $2,000 kg$ is lifted up a distance of $30 m$ by a crane in $1\ minute$. A second crane does the same job in $2\ minutes$. The power supplied by second crane is:
Question 18 :
A man weighing 600 N carries a load of 150 N up the stairs 6 m high in 15 seconds. His power will be:
Question 19 :
An engine develops 10 kW of power. How much time will it take to lift a mass of 200kg to a height of 40m (g = 10 $ms^{-2}$)?
Question 20 :
A machine gun fires $420$ bullets $per\ minute$. The velocity of each of the bullets is $300 m s^{-1}$ and the mass of each bullet is $1 gm$. The power of machine gun is:
Question 21 :
Avinash can run with a speed of $8 \:m \:s^{-1}$ against the frictional force of 10 N, and Kapil can move with a speed of $3 \:m \:s^{-1}$ against the frictional force of 25 N. Who is more powerful?<br>
Question 22 :
The distance from the surface of the earth at which above and below the surface acceleration due to gravity is same will be
Question 23 :
A lamp rated $20w$ and an electric iron rated $50w$ are used for $2$ hour everyday. Calculate the total energy consumed in $20 days.$
Question 24 :
What should be the power of an engine required to lift 90 metric tonnes of coal per hour from a mine whose depth is 200 m?<br>
Question 25 :
A truck of mass $30,000\ kg$ moves up an inclined plane of slope $1$ in $100$ at a speed of $30\ km/h$. The power of the truck is $ \left( Given\ g=10\ ms^{ -1 } \right) $
Question 26 :
A water pump raises $50$ litres of water through a height of $25 \ m$ in $5 \ s$. Calculate the power which the pump supplies. (Take $g=10N$ $kg^{-1}$ and density of water $=1000 \ kgm^{-3}$)
Question 27 :
A machine lifts a load of 2 tonnes weight with an effort of 100 kg weight. When the effort moves through 5 m the load moves through 0.2 m. The efficiency of the machine is
Question 29 :
An electric motor operates with an efficiency of $90$%. A pump operated by the motor has an efficiency of $80$%. The overall efficiency of the system is:
Question 30 :
A crane can lift a box of 600 kg mass to a height of 20 m in 2 minutes. Calculate the power at which the crane is operating ?<br/>
Question 31 :
A pendulum of mass $1\ kg$and length $l = 1\,{\text{m}}$ is released from rest at angle $\theta = \,{60^ \circ }$ . The power delivered by all the forces acting on the bob at the angle $\theta = \,{30^ \circ }$ will be $\left( {g = 10\,{\text{m/}}{{\text{s}}^2}} \right)$.
Question 32 :
A communication satellite of earth which takes $24 hr$. to complete one circular orbit eventually has to be replaced by another satellite of double mass. If the new satellites also has an orbital time periodof $24 hrs$, then what is the ratio of the radius of thenew orbit to the original orbit ?
Question 33 :
An engine develops $10kW$ of power. How muchtime will it take to lift a mass of $200\ kg$ to aheight of $40 \m$. [$g= 10ms^{-2}$]
Question 35 :
A body of mass 5 kg traverses in successive seconds distance of 8,9 and 10 metres. The force acting acting on it is
Question 36 :
Kilowatt is the unit of electrical _______ but kilowatt-hour is the unit of electrical _______.<br/>
Question 37 :
If the power of a motor is $40kW$, at what speed can it raise a load of $20,000N$?
Question 38 :
A body is moving around sun in an elliptical orbit.The maximum and minimum distance are$3 \times 10^{12} m \,\, and \,\, 2 \times 10^{10}m$. The velocity at minimumdistance is $2 \times10^7 m/sec$. Find the velocity of thebody at maximum distance.
Question 39 :
If voltage across a bulb rated $220$V-$100$W drops by $2.5\%$ of its rated value, the percentage of the rated value by which the power would decrease is
Question 40 :
Two men with weights in the ratio $4 : 3$ run up a staircase in time in the ratio $12 : 11$. The ratio of power of the first to that of second is:
