Zigya Logo

Chapter Chosen

Work, Energy and Power

Book Chosen

Physics Part I

Subject Chosen

Physics

Book Store

Download books and chapters from book store.
Currently only available for.
CBSE Gujarat Board Haryana Board

Previous Year Papers

Download the PDF Question Papers Free for off line practice and view the Solutions online.
Currently only available for.
Class 10 Class 12

A block of mass 10 kg, moving in the x-direction with a constant speed of 10 ms-1 , is subjected to a retarding force F= 0.1x J/m during its travel from x = 20 m to 30 m. Its final KE will be

  • 475 J

  • 450 J

  • 275 J

  • 250 J 


A.

475 J

From work energy theorem
work done = change in KE

⇒ W = Kf -Ki
rightwards double arrow space straight K subscript straight f end subscript space equals space straight W space plus straight K subscript straight i space end subscript equals space integral subscript straight x subscript 1 end subscript superscript straight x subscript 2 end superscript Fxdx space plus 1 half mv squared
equals integral subscript 20 superscript 30 minus 0.1 space straight x space dx space plus 1 half space straight x space 10 space straight x space space 10 squared
space equals space minus 0.1 open square brackets straight x squared over 2 close square brackets subscript 20 superscript 30 space plus 500
equals negative 0.50 left square bracket 30 squared minus 20 squared right square bracket space plus 500
equals negative 0.05 left square bracket 900 minus 400 right square bracket plus 500
rightwards double arrow space straight K subscript straight f equals negative 25 plus 500 equals 475 space straight J

From work energy theorem
work done = change in KE

⇒ W = Kf -Ki
rightwards double arrow space straight K subscript straight f end subscript space equals space straight W space plus straight K subscript straight i space end subscript equals space integral subscript straight x subscript 1 end subscript superscript straight x subscript 2 end superscript Fxdx space plus 1 half mv squared
equals integral subscript 20 superscript 30 minus 0.1 space straight x space dx space plus 1 half space straight x space 10 space straight x space space 10 squared
space equals space minus 0.1 open square brackets straight x squared over 2 close square brackets subscript 20 superscript 30 space plus 500
equals negative 0.50 left square bracket 30 squared minus 20 squared right square bracket space plus 500
equals negative 0.05 left square bracket 900 minus 400 right square bracket plus 500
rightwards double arrow space straight K subscript straight f equals negative 25 plus 500 equals 475 space straight J

3986 Views

Define watt.

Power is said to be one watt if one joule of work is done in one second. 
860 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 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

1.png
curious learner
Do a good deed today
Refer a friend to Zigya