Sally and sue were investigating the topic of friction in science. they used a small car and a ramp as seen in the picture to test what they were learning. they knew that they slipped easily on waxed floors but not on carpet, so they decided to change the material on the surface of the ramp to see what happened. they planned to use glass, carpet, aluminum foil, and sandpaper and run the car down the ramp over each surface.
what would be the best research question to guide the girls' experiment?
a) does the amount of surface area affect the friction on the moving car?
b) will the car travel fastest on the glass surface?
c) how does the angle of the ramp affect the speed of the car?
d)do rougher surfaces tend to create more friction than smooth surfaces?

D) Do rougher surfaces tend to create more friction than smooth surfaces?

Explanation:

Friction acts when either there is tendency or actually relative motion between two surfaces in contact. It depends upon the area of contact surface and roughness of the surfaces. More the area and roughness, more friction would be there. More friction would mean more force would be required to cause the relative motion between the two surfaces.

Here, sally and sue are changing the surface over ramp on which car moves. The surface area is same. The angle is same and the speed of the car is also same. So, the best research question to guide the girls' experiment would be D) Do rougher surfaces tend to create more friction than smooth surfaces?

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.