Guide
Pulley - Instead of an axle, a wheel could also rotate a rope, cord, or belt. This variation of the wheel
and axle is the pulley. In a pulley, a cord wraps around a wheel. As the wheel rotates, the cord moves
in either direction. Attach a hook to the cord, and now you can use the wheel’s rotation to raise and
lower objects, making work easier. On a agpole, for example, a rope is attached to a pulley to raise
and lower the ag more easily.
Screw - When you wrap an inclined plane around a cylinder, its sharp edge becomes another simple
tool: a screw. If you put a metal screw beside a ramp, it may be hard to see similarities, but a screw is
actually just another kind of inclined plane. One example of how a screw helps you do work is that it
can be easily turned to move itself through a solid space like a block of wood.
When a pendulum is started, it swings (accelerates) down under the inuence of gravity. Gravity is
the attraction between two masses, such as the earth and an object on its surface. At the bottom of
its arc, the pendulum then swings up on the other side. It continues to move up (and decelerate) until
it stops. The pendulum then begins to swing back down, reaching some maximum velocity at the
bottom of its arc before swinging back up to where it began. The pendulum has gone through one
complete cycle of its motion, and because it is a repetitive cycle, it can be said to be simple harmonic
motion. Friction (the force that resists motion through the rubbing of one object against another) will
eventually stop the pendulum, but not before several cycles have passed.
Simple Motion: The Pendulum
Simple Motion (more fully known as Simple
Harmonic Motion) is what happens when an
object moves in a non-complex periodic way.
This means that:
- The object experiences a force that moves it
- The movement occurs, reaching some
maximum value
- The object returns to its “original” conditions
- The process repeats
Let’s take the example of a pendulum and
consider what happens. A pendulum is defined
as a body suspended from a fixed point so that
it can swing back and forth under the influence
of gravity as a force.
D.3
D.4
cont.