Question

charlie is investigating friction. she will use the same amount of force to push two wooden balls across two level surfaces. then she will record her results in the table below.

trial	ball	weight	surface	distance ball moved
2	x	1 lb	pavement
3	y	2 lb	polished tile
4	y	2 lb	pavement

which prediction will most likely describe how friction will affect her findings?
the distance for trial 3 will be greater than the distance for trial 1 partly because the weight difference of the balls will affect friction.
the distance for trial 2 will be greater than the distance for trial 1 because the difference in surface roughness will affect friction.
the distance for trial 4 will be greater than the distance for trial 2 partly because the weight difference of the balls will affect friction.
the distance for trial 3 will be greater than the distance for trial 4 because the difference in surface roughness will affect friction.

Explanation:

Friction is affected by surface roughness and the normal force (related to weight). A smoother surface has less friction and allows the ball to move further. A heavier ball exerts more normal - force and experiences more friction. In Trial 1 and 3, the surface is the same (polished tile), but the ball in Trial 3 is heavier, so it will experience more friction and move less. In Trial 1 and 2, the ball is the same weight, but pavement is rougher than polished tile, so the ball in Trial 2 will experience more friction and move less. In Trial 2 and 4, the surface is the same (pavement), and the ball in Trial 4 is heavier, so it will experience more friction and move less. In Trial 3 and 4, the ball is the same weight, but polished tile is smoother than pavement, so the ball in Trial 3 will move further than the ball in Trial 4.

Answer:

The distance for Trial 3 will be greater than the distance for Trial 4 because the difference in surface roughness will affect friction.