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Work, Energy and Power

Physics Part I

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Class 10 Class 12
A body is initially at rest. It undergoes one-dimensional motion with constant acceleration. The power delivered to it at time t is proportional to,
• (i) t1/2

• (ii) t

• (iii) t 3/2

• (iv) t2

B.

(ii) t

Tips: -

From,

v = u + at

v = 0 + at = at

As power, P = F × v

∴            P = (ma× at = ma2t

As m and a are constants, therefore, P ∝ t
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What is watt?

SI unit of power is Watt.
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Is work a scalar or a vector quantity?

Work is dot product of two vectors. i.e. .

And dot product is a scalar quantity. Therefore, work is a scalar quantity.
1450 Views

Define the unit joule.

Work done is said to be one joule if one newton of  force displaces the body through a distance of one meter in the direction of applied  force .
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What are different units of energy?

The different units of energy are :

(i) Joule
(ii) Erg
(iii) eV
(iv) KWh
(v) Calorie.

804 Views

Define watt.

Power is said to be one watt if one joule of work is done in one second.
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