2. a woman prevents a 3kg brick from falling by pressing it against a vertical wall. the coefficient of friction
is 0.6
a what force must she use?

Explanation:

The downward force is the weight of the block which can be calculated by W = mg = 3×10 = 30 N

So the frictional force must be equal to 30 N to prevent the block from fall.

So to calculate the normal reaction ( the force exerted by the women)

F = xR

Where F = frictional force

x = coefficient of friction

R = normal reaction.

By substituting you can get,

30 = 0.6× R

R = 50 N

iron would move it is magnetic there is a mag field around the current in the wire