Which of these actions will increase friction? check all that apply.
scratching a surface to make it rougher
polishing a surface to make it smoother
increasing the size of a flying object
adding extra weight to an object
placing oil between two surfaces

scratching a surface to make it rougher

increasing the size of a flying object

adding extra weight to an object

Explanation:

Friction exists between two surfaces when they are or tend to be in relative motion. This happens due to the interlocking of the microscopic hills and valleys structure of the two surfaces. Friction depends on the roughness of the surface. If a surface is scratched, it can be made more rough and thus, friction would increase. Polishing or oiling the surfaces can reduce friction between them. Friction can also be increased by increasing the weight of the object. It is difficult to move a heavier body. also, with increase in the contact surface, friction increases. Therefore, if the size of a flying object is increased, air drag increases.

the answer is b i think

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000