Q4 of 33 Page 156

Define average power.

When a machine or person does different amounts of work or uses energy in different intervals of time, the ratio between the total work or energy consumed to the total time is average power.

Average Power =


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2

Define 1 watt of power.

 3

A lamp consumes 1000 J of electrical energy in 10 s. What is its power?

 1

Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’:

(a) Suma is swimming in a pong.


(b) A donkey is carrying load on its back.


(c) A wind-mill is lifting water from a well.


(d) A green plant is carrying out photosynthesis.


(e) An engine is pulling a train.


(f) Food-grains are getting dried in the sun.


(g) A sailboat is moving due to wind energy.

 2

An object thrown at a certain angle to the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. What is the work done by the force of gravity on the object?