Problems:


Here is the URL for the Washington
Monument. Go to the web site to retrieve the information for part
A.

If 1 meter = 3.28
feet, what is the height of the Washington Monument in meters?

A worker assigned
to the restoration of the Washington Monument is checking the condition
of the stone at the very top of the monument. A nickel with a mass
of 0.005 kg is in her shirt pocket. What is the gravitational potential
energy (GPE) of the nickel at the top of the monument?

What is the kinetic
energy (KE) of the nickel in her shirt pocket at the top of the
monument?

If the nickel accidentally
falls out of her pocket, what will happen to the gravitational potential
energy (GPE) of the nickel as it falls to the ground?

If the nickel accidentally
falls out of her pocket, what will happen to the kinetic energy
(KE) of the nickel as it falls to the ground?


Consider the concepts
of kinetic energy (KE) and gravitational potential energy (GPE) as
you complete these questions. A ball is held 1.4 meters above the
floor. Use the terms KE of GPE as your answers.

When the ball is held
motionless above the floor, the ball possesses only ?
energy.

If the ball is dropped,
its ?
energy decreases as it falls.

If the ball is dropped,
its ? energy
increases as it falls.

In fact, in the absence
of air resistance, the amount of ?
energy when the ball is held motionless above the floor equals the
amount of ?
energy at impact with the floor.


We will now use energy
considerations to find the speed of a falling object at impact. Artiom
is on the roof replacing some shingles when his 0.55 kg hammer slips
out of his hands. The hammer falls 3.67 m to the ground. Neglecting
air resistance, the total mechanical energy of the system will remain
the same. The kinetic energy and the gravitational potential energy
possessed by the hammer 3.67 m above the ground is equal to the kinetic
energy and the gravitational potential energy of the falling hammer
as it falls. Upon impact, all of the energy is in a kinetic form. The
following equation can be used to represent the relationship:
GPE + KE _{(top)}
= GPE + KE _{(at impact) }
Because the hammer is dropped
from rest, the KE at the top is equal to zero.
Because the hammer is at base level, the height of the hammer is equal
to zero; therefore the PE upon impact is zero.
We may write our equation
like this:
GPE _{(top)} = KE _{(at impact)}
This gives us the equation:
( mgh) _{(top)}
= 1/2 mv^{2} _{(at impact)}

Notice that the mass
of the hammer "m" is shown on both sides of the equation.
According to the math rules we have learned, what does this mean?

Manipulate the equation
(rearrange the variables) to solve for v. (Remember that manipulating
an equation does not involve numbers and substitutions. You just
rearrange the equation. v = ?)

Use your equation
from part B to find the speed with which the hammer struck the ground.
