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Work, Energy and Power

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Physics Part I

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Physics

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12

On a frictionless surface, a block of mass M moving at speed v collides elastically with another block of same mass M which is initially at rest. After collision, the first block moves at an angle θ to its initial direction and has a speed v/3/ The second block's speed after the collision is 

  • fraction numerator 2 square root of 2 over denominator 3 end fraction space v
  • 3/4 v

  • fraction numerator 3 over denominator square root of 2 end fraction space straight v
  • fraction numerator square root of 3 over denominator 2 end fraction straight v

A.

fraction numerator 2 square root of 2 over denominator 3 end fraction space v

According to law of conservation of kinetic energy, we have

1 half Mv squared space plus 0 space equals space 1 half straight M open parentheses straight v over 3 close parentheses squared space plus space 1 half Mv subscript 2 superscript 2

rightwards double arrow space straight v squared space equals space straight v squared over 9 space plus straight v subscript 2 superscript 2

rightwards double arrow space straight v squared space minus fraction numerator straight v squared over denominator space 9 end fraction space equals space straight v subscript 2 superscript 2 space rightwards double arrow space fraction numerator 8 straight v squared over denominator 9 end fraction
Velocity space of space second space block space after space collision space straight v subscript 2 space equals space fraction numerator 2 square root of 2 over denominator 3 end fraction straight v

According to law of conservation of kinetic energy, we have

1 half Mv squared space plus 0 space equals space 1 half straight M open parentheses straight v over 3 close parentheses squared space plus space 1 half Mv subscript 2 superscript 2

rightwards double arrow space straight v squared space equals space straight v squared over 9 space plus straight v subscript 2 superscript 2

rightwards double arrow space straight v squared space minus fraction numerator straight v squared over denominator space 9 end fraction space equals space straight v subscript 2 superscript 2 space rightwards double arrow space fraction numerator 8 straight v squared over denominator 9 end fraction
Velocity space of space second space block space after space collision space straight v subscript 2 space equals space fraction numerator 2 square root of 2 over denominator 3 end fraction straight v
2538 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 .
799 Views

Is work a scalar or a vector quantity?

Work is dot product of two vectors. i.e. F with rightwards arrow on top times S with rightwards arrow on top.

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

What is watt?

SI unit of power is Watt. 
773 Views

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. 
860 Views