Chapter 9 - Energy Flashcards

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1
Q

Work is the product of what two variables?

A

The net force acting on a object and the distance through which it is moved.

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2
Q

What is power?

A

The rate at which work is done (or work divided by time)

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3
Q

What are the two forms of mechanical energy we studied?

A

Kinetic energy and gravitational potential energy

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4
Q

What is the unit of work and energy?

A

The joule (or Newton-meter)

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5
Q

What is the unit of power?

A

The watt (or joule/sec)

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6
Q

What is kinetic energy?

A

The energy an object has as a result of its motion.

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7
Q

The kinetic energy of a moving object is equal to …

A

The work required to bring it to its speed from rest, or the work the object can do while being brought to rest.

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8
Q

The law of conservation of energy states that energy cannot be ______ or _______. Instead, its transformed from one form to another.

A

Created or destroyed.

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9
Q

What are the six simple machines?

A

Pulley, wheel and axle, inclined plane, screw, wedge and lever.

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10
Q

The trade off of using less force with a simple machine is what?

A

Having to exert that force over a greater distance.

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11
Q

A machine’s efficiency is equal to ________

A

the ratio of useful work output to total work input

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12
Q

In a complex pulley system, the mechanical advantage equals ________

A

the number of supporting cables.

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13
Q

If a boulder on the edge of a cliff has 100 J of potential energy, how much kinetic energy will it have when it’s fallen three-quarters of the way to the bottom?

A

75 Joules

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14
Q

Why can a machine not be 100% efficient?

A

Loss of energy due to friction.

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