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**3**

If a motor lifts the water

from a depth ‘h1’ and then

raises to a height ‘h2’ then

the power of the motor is

given by

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Slide 17

Power of heart = work/time

= (F.s)/t

= (PxA.s)/t

= (PxV )/t

= (hdgV)/t

(P = pressure,A = area of vessel, V = volume of vessel and

s = length of the vessel)

Thus power of heart = P(V/t) = (hdgV)/t

= Pressure x volume of blood pumped per second

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Slide 18

The heart of a man pumps 4 litres of blood per minute at a pressure of 130 m.m. of Hg. If the density of the blood is 13.6 gm/c.c. calculate the power of the heart.

Solution:-

Power of heart = (hdgV)/t

= 1.155watt.

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Slide 19

Power of lungs =

(mass of air blown per second ) x (velocity)2

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Slide 20

The work done by from time t1 to time t2 is given by

Where P = F.v

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W

Slide 21

If force F acted on a body of mass ‘m’ which is at rest , then the power produced in that body in time ‘t’ is given by

P = F.v

= F(F/m)t

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V = u + at

= 0 + at

= at

= (F/m)t

P

P = Fv

= mav

= ma(at)

= ma2t

Slide 22

A box of mass ‘m’ moved along a straight line by a machine delivering constant power(P).Then the distance moved by the body in terms of m, P & t is given by

Solution:- P=Fv = mav

P= m(dv/dt)v

vdv = (P/m)dt ,by integrating we get

dx/dt

On integrating we get,

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Slide 23

Electrical power

Instantaneous electrical power

The instantaneous electrical power P delivered to a component is given by

P(t) = V(t).I(t)

where P(t) is the instantaneous power, measured in watts (joules per second)

V(t) is the potential difference (or voltage drop) across the component, measured in volts

I(t) is the current through it, measured in amperes

If the component is a resistor, then:

P = V.I = I2 .R

where R is the resistance, measured in ohms.

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- Introduction
- Definition
- Average and instantaneous power
- Units of power
- Alternative formulae for power
- Special cases
- Quiz
- Power of motor
- Power of heart
- Heart problem
- Power of lungs
- Work in terms of power
- Power
- Electrical power
- Average electrical power for sinusoidal voltages
- Average electrical power for sinusoidal voltages
- Average electrical power for AC
- Power in optics
- Power of wave
- Summary

- Friction
- Direct heat utilization of geothermal energy
- Practical Applications of Solar Energy
- Solar Energy
- Newton’s Law of Gravity
- Buoyancy
- Sensory and Motor Mechanisms

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