Simple Machines

Lesson 19

What You Will Learn✹ How can you make doing a job, such as

lifting a heavy box, easier? ✹ In this lesson, you will investigating a number

of simple machines and learn how they make work easier.

✹ You will identify the six simple machines. ✹ You will also determine the amount of work

needed to do work using the simple machines.

Work and Force✹ https://gizmodo.com/a-brief-history-of-

physics-1147115801 ✹ In science, work is defined as a force

moving an object over a distance. ✹ A force is a push or pull. ✹ When you push a shopping cart, kick a

ball, or lift a heavy box, you are doing work.

Work ✹ Work is done only if an object moves. ✹ If you hold a heavy object steady above

the ground, you are not doing work, even though your arms may get tired.

✹ If you lift the box a fraction of an inch, you are doing work.

The 6 Simple Machines-a simple machine is a device that makes work easier and that has few or no moving parts.

LeverPulley Wheel and Axle

WedgeScrewInclined Plane

Simple Machines ✹ Simple machines make work easier by

changing the size or direction or both of the force used to do the work.

✹ A simple machine does not allow you to do less work.

✹ It just makes the work easier for you to do. ✹ The equation for work is

✹ Work=force X distance ✹ W=Fd

W=Fd✹ In this equation, work will stay the same

while force is reduced as distance increases.

✹ A simple machine can decrease the force needed to move an object, but force must be applied over a greater distance.

Energy: Ability to do work

Work: Force x Distance

Force: A Push or a Pull

Definitions:

Inclined Plane

Inclined Planes✹ An inclined plane is a

flat surface that is higher on one end

✹ Inclined planes make the work of moving things easier

✹ A ramp is an example of an inclined plane

Inclined Plane✹ It is easier to push an

object up a ramp than it is to lift the same object straight up to the same height.

✹ Increasing the distance decreases the force needed to so the same amount of work.

Screw

• When a screw is turned, a small force is applied over the long distance of the screw’s threads.

• This makes the work of moving the screw into a board easier.

• This is similar to driving around a mountain to get to the top as opposed to driving straight up.

Wedges✹ Two inclined planes

joined back to back. ✹ Wedges are used to

split things. ✹ A wedge changes the

direction of a force. ✹ Wedges transfer force

in one direction into a force in two directions.

Levers ✹ A lever is a simple machine made up of a

bar that pivots at a fixed point called a fulcrum.

✹ The force applied to a lever is called the effort.

✹ The object moved is the load. ✹ A lever allows a person to move a large

load with relatively little force. ✹ As force is applied to one end, the other

end moves in the opposite direction.

Levers.

✹ Common examples of levers include crowbars, scissors, pliers, tin snips, and seesaws.

Levers✹ Other examples of

levers include wheel barrows, doors, and bottle openers.

Pulleys✹ A pulley is a rope

wrapped around a wheel. ✹ A pulley needs a rope,

chain or belt around a groove to make it do work.

✹ A load is attached to one end of the rope.

✹ A force is applied to the other end.

WHEEL AND AXLE✹ A wheel and axle consists

of two connected cylinder-shaped objects with different diameters.

✹ The wheel is always larger than the axle.

✹ When an applied force turns the wheel, the axle turns too.

✹ The axle moves a shorter distance than the wheel, so the axle turns with greater force.

✹ A doorknob and a screwdriver are examples of a wheel and axle.

Review✹ Name the six simple machines… ✹ Find three examples of each. ✹ How does each one make work easier? ✹ Sally has an ax that she uses to chop wood.

The metal part chops through the wood, pushing it apart into two smaller sections. Which simple machine is found on the head of the ax?

✹ A wedge

✹ Sally and Sue are across the street on the seesaw. The center of the seesaw is used to balance the board with the seats. The two girls can easily move up and down without much force.

✹ The seesaw is an example of which simple machine?

✹ A lever

✹ The cap on Sam’s water bottle has a spiral shape. When he places it on the bottle and twists, the cap pulls itself toward the bottle.

✹ The bottle cap is an example of which simple machine?

✹ A screw

✹ When you turn the large knob on a door, a rod on the inside releases a latch that holds the door closed. It would be difficult to turn the rod if the knob wasn't attached to it.

✹ The door knob and rod make up which simple machine?

✹ A wheel and axle.

✹ A wheel with a rope is used to hoist a flag up to the top of a tall flagpole. The simple machine can also be used to help lift heavy objects with less force.

✹ The wheel and rope make up which simple machine?

✹ A pully