Machines Do Work

1. How do ___________ make work _________? A __________ is a device that changes a ________. Machines make work ____________ to do. They change the _________ of a force needed, the ________________ of a force, or the ______________ over which a force acts. Machines Do Work

2. Machines Do Work • Each complete rotation of a jack handle applies a __________ force over a ____________ distance. • A small force exerted over a large distance becomes a ____________ force exerted over a ____________ distance. • Each rotation lifts the car only a very short distance.

3. Machines Do Work • Increasing Distance • A rower pulls an oar through a ___________ distance. The end of the oar in the water moves through a ___________ distance. The increased travel of the oar through the water requires the rower to exert a ____________ force. • A machine that _____________ the distance through which you exert a force ____________ the amount of force required.

4. Machines Do Work • Changing Direction • Some machines change the direction of the applied force. ___________ back on the handle of the oar causes its other end to move in the ______________ direction. • Machines can change the amount of force and the distance the force acts through as well as the direction of the force.

5. How are work _________ and work _________ related for a machine? Because of _____________, the work done by a machine is always ________ than the work done on the machine. Work Input and Work Output

6. Work Input and Work Output • Work Input to a Machine • The force exerted on a machine is the _________ force. • The distance the input force acts through is the _____________ distance. • The ___________ input equals the input force multiplied by the input distance.

7. Work Input and Work Output • For an oar, the input force is the force exerted on the handle, and the input distance is the distance the handle moves. • The work input is the work done to move the _________________.

8. Work Input and Work Output • Work Output of a Machine • The force exerted by a machine is called the _______________ force. • The distance the output force is exerted through is the ____________ distance. • The ____________ output of a machine is the output force multiplied by the output distance.

9. Work Input and Work Output • The output work of the oars results from the oars pushing against the water so that the water pushes back against the oars. • Although nearly equal, the output work is less than the input work because of friction. All machines use some amount of input work to overcome _______________.

10. Work Input and Work Output • The only way to increase the work output is to _____________ the amount of work you put _______ the machine. You ___________ get more work out of a machine than you put into it!

11. Assessment Questions • What is the output distance of a machine that requires 2 newtons of force exerted over 6 meters and whose output force is 4 newtons? • 2 meters • 3 meters • 6 meters • 12 meters

12. Assessment Questions • The work output of a machine is always greater than the work input to the machine. TrueFalse