# User Forum

Subject :NSO    Class : Class 8

A man sharpens his knife as shown in the figure. Which of the properties of friction are in use?

(i) Friction helps us to hold objects.
(ii) Friction acts in the opposite direction of motion.
(iii) Friction causes the surfaces in contact to wear away.
(iv) Friction produces heat energy.

A (i) and (ii)
B (i), (iii) and (iv)
C (iii) and (iv)
D All (i), (ii), (iii) and (iv)

## Ans 1:

Class : Class 8
All the properties friction are in use. Hence, the correct one option 'D'.

## Ans 2:

Class : Class 5
The Options Are wrong because only 123 are in use.

## Ans 3:

Class : Class 5
The Options Are wrong because only 123 are in use.

## Ans 4:

Class : Class 7
The Options Are wrong I guess because only (i),(ii)and(iii) are in use

## Ans 5:

Class : Class 8
It's not asking about which properties occur (which would be all of them), it's asking which are in use. And that's only 1, 2, and 3. So the options are wrong

Class : Class 8

## Ans 7:

Class : Class 7
The answer is correct, as when friction occurs, obviously, all of its properties will occur, even if not all of the properties are required. That's... how friction works.