Atextbook on a desk is experiencing a force of gravity of 1.56 newtons.
a. draw a free body diagram of the textbook
b. determine its mass.

m= 0.162kg

Explanation:

a) You would draw a square to represent the textbook, and draw the forces that are acting on it, which is force of gravity (Fg going down), and the normal force (Fn, going up)

b) To find its mass, you would use the equation Fg = mg, where m is mass in kg, and g is acceleration of gravity due to earth (9.8m/s^2), and Fg is force of gravity. We know what g is, and we know Fg (1.56 N), so just plug into the eqn and solve for m:

Fg = mg

1.59 = m (9.8)

m= 0.162kg