1. Work and Simple Machines

2. What is “work”?
In science, the word work has a different meaning than you may be familiar with.
The scientific definition of work is: using a force to move an object a distance.
Both the force and the motion of the object must be in the same direction.

3. Work or NOT?
According to the scientific definition, what is work and what is not?
a teacher lecturing to her class
a mouse pushing a piece of cheese with its nose across the floor

5. Work or NOT?
A scientist delivers a speech to an audience of his peers.
A body builder lifts 350 pounds above his head.
A mother carries her baby from room to room.
A father pushes a baby in a carriage.
A woman carries an 8 pound grocery bag to her car.

6. Answers: A scientist delivers a speech to an audience of his peers. No
A body builder lifts 350 pounds above his head. Yes
A mother carries her baby from room to room. No
A father pushes a baby in a carriage. Yes
A woman carries an 8 pound grocery bag to her car. No

7. History of Work:
Before engines and motors were invented, people had to do things like lifting or pushing heavy loads by hand. Using an animal could help, but what they really needed were some clever ways to either make work easier or faster.

8. Simple Machines
Ancient people invented simple machines that would help them overcome resistive forces and allow them to do the desired work against those forces.

9. Simple Machines The six simple machines are: Lever Wheel and Axle
Pulley
Inclined Plane
Wedge
Screw

10. 1. The Pulley
A pulley is a simple machine that uses grooved wheels and a rope to raise, lower, or move a load.
Pulling down on the rope can lift an object attached to the rope. Work is made easier because pulling down on the rope is made easier due to gravity.

11. Everyday Examples: Pulley

12. 2. The Lever A lever is a stiff bar that rotates around a fixed point.
The fixed point is called the fulcrum.
The bar may be either straight or curved.
In use, a lever has both an effort (or applied force) force and a load (resistant force).

13. Everyday Examples: Lever

14. 3. Wheel and Axle
The wheel and axle is a simple machine consisting of a large wheel rigidly secured to a smaller wheel or shaft, called an axle.
When either the wheel or axle turns, the other part also turns. One full revolution of either part causes one full revolution of the other part.

15. Everyday Examples: Wheel and Axle

16. 4. Inclined Plane An inclined plane is an even sloping surface.
The inclined plane makes it easier to move a weight from a lower to higher elevation.
The trade-off is that an object must be moved a longer distance than if it was lifted straight up, but less force is needed.

17. Everyday Examples: Inclined Plane

18. 5. Wedge
A wedge is two inclined planes joined back to back (sloping surfaces are outward).
The wedge is a modification of the inclined plane. Wedges are used as either separating or holding devices.

19. Everyday Examples: Wedge

20. 6. Screw An inclined plane wrapped around a shaft or cylinder.
This inclined plane allows the screw to move itself or to move an object or material surrounding it when rotated.

21. Everyday Examples: Screw