How can u tell matched forces act on objects?

If an object's speed changes, or if it changes the direction it's moving in,

then there must be forces acting on it. There is no other way for any of

these things to happen.

Once in a while, there may be a group of forces (two or more) acting on

an object, and the group of forces may turn out to be "balanced".  When

that happens, the object's speed will remain constant, and ... if the speed

is not zero ... it will continue moving in a straight line.  In that case, it's not

possible to tell by looking at it whether there are any forces acting on it

There are two forces acting upon the book. One force - the Earth's gravitational pull - exerts a downward force. The other force - the push of the table on the book (sometimes referred to as a normal force) - pushes upward on the book.

Explanation:

I hope this helps, and I hope that you get 100% on your assignment!

answer: the rock sample is a sedimentary rock.

explanation:

it is given that:

mass of rock sample, m = 2.7 g

volume of rock sample,

so, density of rock sample will be

since, the density of rock sample is . hence, the rock sample is a sedimentary rock, whose densities varies between .