You need to know the height of a tower, butdarkness obscures the ceiling. you note thata pendulum extending from the ceiling almost touches the floor and that its period is 36 s. what is the height of the tower?

The towers height is 322m  

Explanation:

We can assume that a simple pendulum hangs from the top of the tower.  

In this case, the length of the pendulum will be the same as the height of the tower.

We will use the next expression then:

Where T is the period, L is the pendulum length and g is the gravity

From the previous expression we will have then that the length will be:

Replacing:

The towers height will be then: 322m

a and b sometimes have a positive value

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.