Simple Machines!

Adventures in ScienceFebruary 4th, 2012

What is a Machine?

The Six Simple Machines

1. Lever2. Pulley3. Inclined plane4. Wedge5. Screw6. Wheel

Who uses simple machines?

What defines a Machine?

Definitions:• An apparatus using or applying mechanical

work to perform a particular task.• A device that transmits or modifies force. In other words…

Machines make work easier by…reducing force!

Machines make work Easier

• Work is how much energy you have to exert to move something against a force for a distance.

Gravity (acceleration)

Mass

Distance

Simple machines do NOT reduce the amount of work

• They make doing that Work easier…• by reducing Force…• in exchange of increasing the Distance.

What are Force, Distance, and Work?

Force = Mass x AccelerationWork = Force x Distance

Gravity (acceleration)

Mass

Distance = 1 meter

= 5 kg

= 10 m/s2

Force = Mass x Acceleration

Gravity (acceleration)

Mass = 5 kg

= 10 m/s2

• How much force do you need to move this block?

• F = m x aF = 5kg x 10m/s2 = 50 N

• We need to exert 50 N of force to move this block!

Newton is a unit of Force!!

•F = m * a•N = kg*m/s2

What if we want to put the block on the table?

• We will need to exert Force for a Distance to put the block on the table. This is Work!

Gravity (acceleration)

Mass

Distance = 1 meter

= 5 kg

= 10 m/s2

Work = Force x Distance• Force = Mass x Acceleration• Work = Mass x Acceleration x Distance

Gravity (acceleration)

Mass

Distance = 1 meter

= 5 kg

= 10 m/s2

• Work = 5kg x 10m/s2 x 1m = 50 J

Joule is a unit of Work!

• W = m * a * d = mad• J = kg * m/s2 * m = kg*m2/s2 = Joule

James Prescott Joule

I am very weak!!!

• I can only exert 5N of Force. • • Could I still put the block on the table?• Yes! • With a simple machine!! •

Introducing the [drum roll]…

Mass

Inclined Plane!!!

Gravity (acceleration)

Mass

Distance

• Before with no Inclined Plane…• I had to counteract all of the acceleration due

to gravity!

The Inclined Plane allows me to push against only a fraction of gravity!

Mass

Gravity (acceleration)

Distance

Here’s the proof:

• F = m * a • F = 5kg * 1 m/s2 = 5 N• BUT!!

Mass

Gravity (acceleration)

Distance = 10 meters

= 5 kg

= 1 m/s2

YAY, I can lift it!

We traded off Force for Distance

• Work = mass * acceleration * distance

Mass

Gravity (acceleration)

Distance = 10 meters

= 5 kg

= 1 m/s2

• Work = 5kg x 1m/s2 x 10m = 50 JI am doing:• the same amount of Work with LESS FORCE!!

Simple Machines

• Make it possible to do the same amount of work• But use less force.

• Therefore:• Simple Machines make Tasks Easier!

The Pulley

• Benefit: – Reduces force to

lift objects.

• Trade-off:– The longer the

rope, the easier to lift

What are some real life examples of Pulleys?

Pulley Activity

The Wheel• Benefit: – Reduces friction associated with sliding

• Trade-off:– The larger the wheel, the lower the friction…– The smoother the ride

What are real-life examples of wheels?

Wheel Activity

The Inclined Plane

• Benefit: – Reduces actionable component of gravity

• Trade-off:– The longer the ramp, the lower the force to ascend

What are some examples of inclined planes?

Inclined Plane Activity

The Screw

• Benefit

• Trade-off

What are some examples of screws?

Screw Activity

The Lever

• Benefit

• Trade-off

What are some examples of Levers?

Lever Activity

What are some examples of Wedges?

The Wedge

• Benefit

• Trade-off

Wedge Activity