02.02.2012 - Simple Machines
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Simple Machines! Adventures in Science February 4 th , 2012
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Adventure in Science is about exploring our world by doing. Each Saturday during the school year we have hands-on sessions hosted by local experts on some aspect of science or engineering that they find exciting or interesting. During these sessions the students get to experiment with the tools or ideas involved to better understand how they really work. Sometimes those ideas can grow into something new and make a difference in the world. Who says science isn't fun? During this session we taught kids about the physics of simple machines. http://www.adventureinscience.org/
Transcript of 02.02.2012 - Simple Machines
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
