Ch. 14 Flashcards Preview

8 Science > Ch. 14 > Flashcards

Flashcards in Ch. 14 Deck (33):
1

A vertical force (does, does not) work on an object that is moving in a horizontal direction.

does not

2

What is the SI unit of work?

joule

3

What is rate of doing work?

Power

4

How do you calculate power?

work/time

5

What is the SI unit of power?

watt

6

__________ is equal to one horsepower.

746 watts

7

Describe what a machine is able to do.

makes work easier

8

The work done by a machine is always less than the work done on a machine. Why?

friction

9

What equation describes work input?

work input= input force x input distance

10

The number of times that a machine increases an input forces is the _________________ of the machine.

mechanical advantage

11

Greater input force is required to move an object along a ramp with a rough surface because a greater force is needed to overcome __________.

friction

12

True or false?
A loading ramp with a rough surface has a greater mechanical advantage than one with a smooth surface.

false

13

A machine's ______________________ is the mechanical advantage in the absence of friction.

ideal mechanical advantage

14

Why is the efficiency of a machine always less than 100% ?

there is always friction present

15

Reducing friction __________ the efficiency of a machine.

increases

16

List the six types of machines.

lever,
wheel and axle,
inclined plane,
wedge,
screw,
pulley

17

List an example of a lever.

Using a screw driver to pry the lid off a paint can

18

What is the fixed point that a lever rotates around?

fulcrum

19

What characteristics levers as first-class, second-class, or third-class?

The position of the lever;
first- between input and output forces
third-between fulcrum and output force
__
second-output force is between input force and fulcrum

20

In science, work is done when a ________ acts of an object in the direction the object moves.

force

21

The ideal mechanical advantage of an inclined plane is the _________________________ divided by________________.

distance along the incline plane,
its change in height

22

Screws with threads that are close together have a greater _______________________.

ideal mechanical advantage

23

What is a compound machine?

a combination of 2+ simple machines that operate together

24

What are some examples of compound machines?

car,
washing machine,
watch

25

What is the equation for efficiency?

work output
___________ x 100%
work input

26

What is one way to determine output distance?

divide output work by output force

27

Where is the input arm located?

an a lever, it is the distance between the fulcrum and the input force

28

What machine increases as its thickness decreases relative to its length?

wedge

29

Where is an input force exerted?

on a jack handle to lift a car

30

What is the distance between the output force and the fulcrum?

output arm

31

What SI unit is used to describe a lightbulb?

watt

32

A slanted surface along which a force moves an object to a different elevation is called what?

inclined plane

33

What is the equation for power?

Work/Time