Year 6 - Sc Note

2.  Machine is any device or tool used to make work easier
 Simple machine is a simple tool used to make the work
easier.
 Examples : wheel and
axle, lever, wedge, pulley, gear, inclined plane and
screw.
 Complex or compound machine has more than two
simple machine working together.
 Examples : bicycles, electric blenders and
wheelbarrows

4.  It consists of a larger wheel that is connected to a
smaller rod called axle.
 They are connected in such way that they rotate
together.
 A wheel and axle is a force magnifier. A small force
applied to the wheel provides a larger force at the axle.
 Wheel and axle are used in many devices for example
screwdriver, roller skate, cross-spanner and water tap.

6.  A lever is a rod that rests and turns about a fixed point.
 A fixed point is called the fulcrum.
 Force is applied at some point of the rod. This force is
called the effort.
 Applying a force to one end of the rigid object causes it to
pivot about the fulcrum, causing a magnification of the
force at another point along the rigid object.
 There are three classes of levers, depending on where the
input force, output force, and fulcrum are in relation to
each other.
 Baseball bats, seesaws, wheelbarrows, and crowbars are
types of levers.

7. Examples:
 Seesaw (also known as a teeter-totter)
 Crowbar
 Pliers (double lever)
 Scissors (double lever)

8. Examples:
 Wheelbarrow
 Nutcracker (double lever)
 The handle of a pair of nail clippers

9.  Examples:
 Human arm
 Tongs (double lever) (where hinged at one end, the
style with a central pivot is first-class)
 Catapult
 Any number of tools, such as a hoe or scythe
 The main body of a pair of nail clippers, in which the
handle exerts the incoming force

10.  An inclined plane is a plane surface set at an angle to
another surface.
 This results in doing the same amount of work by
applying the force over a longer distance.
 The most basic inclined plane is a ramp; it requires
less force to move up a ramp to a higher elevation than
to climb to that height vertically.
 The wedge is often considered a specific type of
inclined plane.

12.  A wedge is a simple machine used to separate two objects,
or portions of objects, through the application of force.
 A wedge is made up of two inclined planes. These planes
meet and form a sharp edge. This edge can split things
apart.
 Wedges are used as either separating or holding devices.
There are two major differences between inclined planes
and wedges. First, in use, an inclined plane remains
stationary while the wedge moves. Second, the effort force
is applied parallel to the slope of an inclined plane, while
the effort force is applied to the vertical edge (height) of the
wedge.

13.  Wedges are used as either separating or holding
devices. A wedge can either be composed of one or two
inclined planes. A double wedge can be thought of as
two inclined planes joined together with their sloping
surfaces outward.
 Examples of wedges are: knives, axes, forks and nails
 The common "door wedge" uses the force on the
surfaces to provide friction, rather than separate
things, but it's still fundamentally a wedge.

16.  A pulley is a wheel with a groove along its edge, where
a rope or cable can be placed.
 It uses the principle of applying force over a longer
distance, and also the tension in the rope or cable, to
reduce the magnitude of the necessary force.
 Complex systems of pulleys can be used to greatly
reduce the force that must be applied initially to move
an object.

18.  Pulleys are used to lift up or lower down objects.
 Pulleys make our work easier by:
1. Changing the direction of a force
2. Lift a load with less effort. The more pulleys use the
lesser the effort is needed.

19.  Gears have many uses in our lives. They are used to :
- multiply or reduce speed and force;
- change the direction of motion
- transmit a force over a distance
 Examples : watch, egg beater, hand drill and gear in a
bicycle
 In a gear train we have a gear known as the driver and
one known as the follower.
Driver - is the gear that has the force or motion input.
Follower - is the gear that results in the force or
motion output.

20.  The gear ratio of a gear train is the number of teeth on
the follower divided by the number of teeth on the
driver. In the gear train above the driver has 18 teeth
while the follower has 8 teeth. Therefore the gear ratio
is 8/18 or 4/9. For every 4 turns of the driver the
follower turns 9 times. This gear train can be used to
multiply speed on a bicycle if the follower was
connected to a wheel and the driver connected to the
paddles.

21.  Low gear ratio = more speed = less force
High gear ratio= less speed = more force

22.  A screw is a simple machine that is made from another
simple machine. It is actually an inclined plane that
winds around itself.
 A screw has ridges and is not smooth like a nail. Some
screws are used to lower and raise things.
 They are also used to hold objects together.
 Screw can be used to fasten or hold things tightly
together or to raise weight
 Examples : corkscrew, screw cap bottle, jackscrew, g
damp

24.  Also known as compound machine.
 Consist of two or more simple machines.
 For example: Scissors is actually combination of a
wedge and a lever
 Watch is combination of gears and wheel and axle
 Hand drill is combination of gear, wedge, wheel and
axle
 Wheelbarrow is combination of lever and wheel and
axle
 Bicycle is combination of levers, wheel and axle, gears
and screws