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7th grade year > science work and machines > Flashcards

Flashcards in science work and machines Deck (47)
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1

What is the formula to find work?

work = force X distance

2

What is the formula to find power?

power = work/time

3

What is the SI unit for work?

joules

4

What is the SI unit for power?

watts

5

What is the formula used to find mechanical advantage?

output force/input force

6

What is the formula used to find the efficiency of a machine?

Eff= (output work/input work) X 100

7

How can you increase the mechanical advantage of an inclined plane or wedge?

increasing its length (inclined plane) or by increasing its length and making it thinner (wedge)

8

How do you calculate the ideal mechanical advantage of a pulley system?

by counting the number of rope sections that are supporting the objects (pulling up)

9

What two machines' mechanical advantages increase when they become longer and thinner?

inclined plane and wedge

10

What is the mechanical advantage of a single, fixed pulley?

MA = 1

11

What is the mechanical advantage of a single, movable pulley?

MA = 2

12

What kind of pulley is shown in the image?

What is its mechanical advantage?

single, movable pulley

MA = 2

13

What kind of pulley is shown?

What is its mechanical advantage?

single, fixed pulley

MA = 1

14

How can you determine if work is being done on an object?

Work is done when the object moves in the direction in which the force is being exerted.

15

A machine works by changing at least one of three factors.  Name the three factors.

1.  A machine can change the amount of force you exert.

2.  A machine can change the distance over which you exert your force.

3.  A machine can change the direction in which you exert your force.

16

What is the difference between a real machine and an ideal machine?

real machines have friction and an efficiency of less than 100%

ideal machines have no friction and an efficiency of 100%

17

Would applying input force to the wheel or the axle provide for smaller input force and larger output force?  Explain why.

Because the wheel is larger than the axle, the axle rotates and exerts a large output force.  The wheel and axle increases your force, but you must exert force over a longer distance.

18

Describe the relationship between friction and the efficiency of a machine.

19

The thermal energy of an object depends upon what three factors?

1.  number of particles

2.  temperature of the object

3.  arrangement of the particles

20

How are work and energy related?

Work is the transfer of energy.

Work requires energy.

21

What is the most common energy transformation between two types of energy?

potential and kinetic

22

How are power and energy related?

Power is the rate at which energy is transferred.

23

What two factors affect kinetic energy?

How is KE changed when these factors are increased or decreased?

mass and velocity

If velocity increases, so does KE

If mass increases, so does KE.

24

What is chemical energy?

Stored potential energy in the bonds (chemical bonds) that hold chemical compounds together

25

What is thermal energy?

the total potential and kinetic energy of the particles in an object

26

What is nuclear energy?

a type of potential energy stored in the nucleus of an atom

27

What is electromagnetic energy?

energy that travels in the form of rays or waves and includes UV rays, X-rays, infrared, microwaves, visible light, radio waves, and gamma rays

28

What is electrical energy?

the energy of moving electrical charges (electrons)

29

What kind of energy do you experience when you eat a peanut butter and jelly sandwich?

chemical energy - in the bonds of the food

30

What is energy transformation?

a change from one form of energy to another