Power

The power required to lift a mass of $8.0 \mathrm{kg}$ up a vertical distance of $4 \mathrm{m}$ in $2 \mathrm{s}$ is (taking acceleration due to gravity as $10 \mathrm{m}/{\mathrm{s}}^2$) :

An electric bulb is rated as $220 \mathrm{V}$ and $80 \mathrm{W}$. When it is operated on $110 \mathrm{V}$, the power rating would be:

The ratio of powers of two motors is $\frac{3\sqrt{x}}{\sqrt{x+1}},$ that are capable of raising $300 \mathrm{kg}$ water in $5$ minutes and $50 \mathrm{kg}$ water in $2$ minutes respectively from a well of $100 \mathrm{m}$ deep. The value of $x$ will be

If the maximum load carried by an elevator is $1400 \mathrm{kg}$ $(600 \mathrm{kg}\text{-Passengers} +800 \mathrm{kg}\text{-elevator})$ , which is moving up with a uniform speed of $3 \mathrm{m} {\mathrm{s}}^{-1}$ and the frictional force acting on it is $2000 \mathrm{N}$, then the maximum power used by the motor is _____________$\mathrm{kW}. \left(g=10 \mathrm{m} {\mathrm{s}}^{-2}\right)$

Which of the following graphs represent constant non zero power?

Found the power delivered by $F$ at $t=10 \mathrm{s}$. The body starts from rest.

Frictional force acting on the lift of mass $1400 \mathrm{kg}$ is $2000 \mathrm{N}$. If lift moves with constant velocity of $3 \mathrm{m} {\mathrm{s}}^{-1}$ in upward direction, the power (in $\mathrm{kW}$) of motor is

(Take $g=10 {\mathrm{ms}}^{-2}$)

A horse pulls a wagon with a force of$360 \mathrm{N}$ at an angle of $60°$ with the horizontal at a speed of $10 \mathrm{km} {\mathrm{hr}}^{-1}$. The power of the horse is

Star$A$ has radius $r$ surface temperature $T$ while star$B$ has radius$4r$and surface temperature $\frac{T}{2}$ The ratio of the power of two stars,$P_A: P_B$is (a) 16:1 (b) 1:16 IMP PMT 200
(d) 14
(c) 1:1

 An electric heater has a rating of $1500 \mathrm{W}- 220 \mathrm{V}.$How much heat will it produce in 15 seconds if it is operated on a supply of $110$Volts?
 

An engine lifts $400 \mathrm{kg}$mass through a height of $100 \mathrm{m}$ in $20 \mathrm{s}$. The rated power of the engine is, if efficiency of engine is $80\%$ (g = $10 {\mathrm{ms}}^{-2}$) 

A force is delivering constant power of $20 \mathrm{W}$ to a body. If the force is acting in the direction of the motion, then the magnitude of force, when velocity is $10 \mathrm{m}/\mathrm{s}$, is 

A car of mass $\mathrm{m}$ is moving along a circular track of radius r with a speed that increases linearly with time $\mathrm{t}$ as $\mathrm{v}=\mathrm{kt}$, where $\mathrm{k}$ is a constant. The instantaneous power delivered by the agent applying the force is  

A force of $20 \mathrm{N}$ act along the direction of motion of a body moving with a speed $5 {\mathrm{ms}}^{-1}$. The instantaneous power delivered by the force is 

A force of $\left(3\hat{\mathrm{i}}+4\hat{\mathrm{j}}+5\hat{\mathrm{k}} \right) \mathrm{N}$ acts on a body for $2 \mathrm{s}$ and produces a displacement of $\left(2\hat{\mathrm{i}}+3\hat{\mathrm{j}}+2\hat{\mathrm{k}}\right)$ m. Calculate the power

If the unit of force were $10 \mathrm{N}$, that of power were $1 \mathrm{MW}$ and that of time were $1 \mathrm{millisecond}$ then the unit of length would be

A block of mass $M$ is allowed to slide down a fixed smooth inclined plane of angle $\theta$ and length $l$. What is the power developed by the force of gravity when the block reaches the bottom?

A car of mass $m$ is moving along a circular track of radius $r$ with a speed which increases linearly with time $t$ as $v=kt$, where $k$ is a constant. The instantaneous power delivered by agent applying the force is

Force acting on a particle varies with the distance travelled by the particle as $F\propto \frac{1}{{\left(x\right)}^{{\displaystyle \frac{1}{3}}}}$ then power due to this force varies with $x$ as :

Dot product $\overrightarrow{F}.\overrightarrow{v}$ is equal to: