Ravi suggested his friend Karim the following ways to reduce or minimise friction. (i) Smoothening the surfaces in contact. (ii) applying lubricants between the surfaces (iii) streamlining the bodies of objects moving in fluids (iv) Applying coarse material between the surfaces is contact. Which of the methods suggest is correct? Options :
(i) and (iv)
only (iv)
(ii) and (iii)
(i), (ii) and (iii)

3rd option

Explanation:

According to modern theory of friction, friction cannot be reduced by making smooth. example two mirrors are smooth but if kept in contact there is very high friction. It is due to intermolecular force of attraction but not roughness.

But if you go towards old theory then last option is correct as friction is due to roughness

the independent variable, the one that is intentionally manipulated, is whether or not the car hits the barrier.

the dependent variable, the one that you measure the response in, is the distance that the washers travel.

the earths atmosphere is made up of nitrogen and oxygen. solids can turn into gasses through a process called sublimation. sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase.

hope this : d