What kind of ground surface (cover, wood, tile, tile, and so on.) makes the most or the least grinding? (More youthful children may test this by rolling a ball or toy truck over various surfaces. More seasoned children can utilize a spring scale to quantify the power of grating. Use toy vehicles or a dynamic truck to test what sway expanded mass has on speed. What are the subsequent speeds after a moving and unmoving item impact? Shouldn't something be said about two moving articles in same or distinctive ways?