Question

18. Read the following and answer any four questions:

A more powerful vehicle would complete a journey in a shorter than a less powerful one. The speed with which

these vehicles change the energy or do not is a basis for their time to complete the journey. Power measures the

speed of work done, that is, how fast or slow work is done. The power of an agent may vary with time. This

means that the agent may be doing work at different intervals of time. If this machine is used continuously for

one hour. It will consume 1kW h of energy. Thus, 1 kW h is the energy used in one hour at the rate of

1000 js – 1

s

– 1. The energy used in households, industries and commercial establishments are usually expressed

in kilowatt hour.

(i) SI unit of power is

(a) Watt (b) Joule (c) Newton (d) Meter

(ii) Power is defined as

(a) The rate of doing work (b) the rate of transfer of energy (c) Both (a) and (b) (d) Neither (a) and (b)

(iii) 1 watt is equal to work at rate of

(I) 1 Joule per second (II) 1 Joule per hour (III) 1 Joule per minute (IV) 4 Joule per hour

Choose the correct option among the following

(a) Only (I) (b) (I) and (II) (c) (II) and (III) (d) (II) and (IV)

(iv) An electric bulb of 60W is used for 6h per day. Calculate the ‘units’ of energy consumed in one day by the

bulb.

(a) 0.76 unit (b) 0.36 unit (c) 0.98 unit (d) 0.76 unit

(v) Which of the following statement are incorrect?

(I) A bird sitting on tree possess potential energy only (II) A stationery object may have energy

(III) A flying bird has kinetic energy

(IV) An aeroplane running on the run-way possess kinetic and potential energy both

(a) III and IV (b) I and II (c) II and III (d) II and IV
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Answer 1

Answer:

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Answer 2

– 1. The energy used in households, industries and commercial establishments are usually expressed