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/

1. Simple Machines!
Adventures in Science
February 4th, 2012

2. What is a Machine?

3. The Six Simple Machines
1.
2.
3.
4.
5.
6.
Lever
Pulley
Inclined plane
Wedge
Screw
Wheel

4. Who uses simple machines?

5. 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!

6. Machines make work Easier
• Work is how much energy you have to exert to
move something against a force for a distance.
Distance
Mass
Gravity (acceleration)

7. Simple machines do NOT reduce the
amount of work
• They make doing that Work easier…
• by reducing Force…
• in exchange of increasing the Distance.

8. What are Force, Distance, and Work?
Force = Mass x Acceleration
Work = Force x Distance
Distance
Mass
Gravity (acceleration)
= 1 meter
= 5 kg
= 10 m/s2

9. Force = Mass x Acceleration
• How much force do you need to move this
block?
• F=mxa
F = 5kg x 10m/s = 50 N
• We need to exert 50 N of force to move this
block!
2
Mass
Gravity (acceleration)
= 5 kg
= 10 m/s2

10. Newton is a unit of Force!!
•F = m * a
2
•N = kg*m/s

11. 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!
Distance
Mass
Gravity (acceleration)
= 1 meter
= 5 kg
= 10 m/s2

12. Work = Force x Distance
• Force = Mass x Acceleration
• Work = Mass x Acceleration x Distance
• Work = 5kg x
10m/s
x 1m =
2
Distance
Mass
Gravity (acceleration)
50 J
= 1 meter
= 5 kg
= 10 m/s2

13. Joule is a unit of Work!
• W = m * a * d = mad
• J = kg * m/s2 * m = kg*m2/s2 = Joule
James Prescott
Joule

14. 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!!


15. Introducing the [drum roll]…
Inclined Plane!!!
Mass

16. • Before with no Inclined Plane…
• I had to counteract all of the acceleration due
to gravity!
Distance
Mass
Gravity (acceleration)

17. The Inclined Plane allows me to push
against only a fraction of gravity!
Distance
Mass
Gravity (acceleration)

18. Here’s the proof:
• F=m*a
• F = 5kg * 1 m/s2 = 5 N
• BUT!!
Distance = 10 meters
Mass
Gravity (acceleration)
= 5 kg
= 1 m/s2
YAY, I can lift it!

19. We traded off Force for Distance
• Work = mass * acceleration * distance
• Work = 5kg x
1m/s x
10m =
2
50 J
I am doing:
• the same amount of Work with LESS FORCE!!
Distance = 10 meters
Mass
Gravity (acceleration)
= 5 kg
= 1 m/s2

20. Simple Machines
• Make it possible to do the same amount of work
• But use less force.
• Therefore:
• Simple Machines make Tasks Easier!

21. The Pulley
• Benefit:
– Reduces force to
lift objects.
• Trade-off:
– The longer the
rope, the easier
to lift

22. What are some real life examples of
Pulleys?

23. Pulley Activity

24. The Wheel
• Benefit:
– Reduces friction associated with sliding
• Trade-off:
– The larger the wheel, the lower the friction…
– The smoother the ride

25. What are real-life examples of wheels?

26. Wheel Activity

27. The Inclined Plane
• Benefit:
– Reduces actionable component of gravity
• Trade-off:
– The longer the ramp, the lower the force to ascend

28. What are some examples of inclined
planes?

29. Inclined Plane Activity

30. The Screw
• Benefit
• Trade-off

31. What are some examples of
screws?

32. Screw Activity

33. The Lever
• Benefit
• Trade-off

34. What are some examples of
Levers?

35. Lever Activity

36. What are some examples of
Wedges?

37. The Wedge
• Benefit
• Trade-off

38. Wedge Activity