True/False
Indicate whether the
statement is true or false.
|
|
|
1.
|
When a machine is used to do work, the force applied by the machine is called
the effort force.
|
|
|
2.
|
Under certain conditions, it is possible to get more work out of a machine than
you put into it.
|
|
|
3.
|
Some machines don't multiply the force that is applied to them.
|
|
|
4.
|
Examples of all three classes of levers are found in the human body.
|
|
|
5.
|
In order for work to be done on a object, the object must move.
|
Multiple Choice
Identify the
choice that best completes the statement or answers the question.
|
|
|
6.
|
A device that makes work easier by changing the size or direction of force is
called what?
a. | power | c. | machine | b. | watt | d. | force |
|
|
|
7.
|
What is the work that you do on a machine called?
a. | power | c. | work output | b. | work input | d. | lever |
|
|
|
8.
|
What is the number of times the machine multiplies force called?
a. | power | c. | mechanical efficiency | b. | output
force | d. | mechanical
advantage |
|
|
|
9.
|
Which of the following is a comparison of a machine’s work output with the
work input?
a. | mechanical efficiency | c. | mechanical advantage | b. | force | d. | power |
|
|
|
10.
|
Which equation would you use to find mechanical advantage?
a. | MA = work output/work input x 100 | c. | MA = work
input/work output x 100 | b. | MA = output force/input
force | d. | MA =
input force/output force |
|
|
|
11.
|
Which of the following prevents machines from being 100% efficient?
a. | friction | c. | output force | b. | input force | d. | power |
|
|
|
12.
|
In which situation is a person doing work on an object?
a. | A school crossing guard raises a stop sign that weighs 10 N. | b. | A student walks
while wearing a backpack that weighs 15 N. | c. | A man exerts 350 N force on a rope attached to
a house. | d. | A worker holds a box 1 m off the floor. |
|
|
|
13.
|
If a barbell weighs 160 N, what other information do you need to calculate how
much work it takes to lift it?
a. | the shape of the weights | b. | how high the barbell is being
lifted | c. | the strength of the person doing the lifting | d. | the amount of output
force |
|
|
|
14.
|
What type of simple machine is a screw?
a. | inclined plane | c. | lever | b. | wheel and axle | d. | pulley |
|
|
|
15.
|
What is it called when a force causes an object to move in the direction of the
force?
a. | energy | c. | work | b. | force | d. | power |
|
|
|
16.
|
What is a machine that is made of two simple machines called?
a. | simple machine | c. | pulley | b. | lever | d. | compound
machine |
|
|
|
17.
|
What is a machine with a grooved wheel that holds a cable called?
a. | lever | c. | wheel and axle | b. | pulley | d. | wedge |
|
|
|
18.
|
Which of the following would increase the mechanical advantage of a first-class
lever?
a. | applying a greater input force | b. | increasing the rate at which force is
applied | c. | decreasing the load | d. | moving the fulcrum closer to the
load |
|
|
|
19.
|
Chris and Jane are lifting boxes to put them on shelves. Chris does 200 J of
work in 5 min, and Jane does 200 J of work in 4 min. What is the difference between the two
jobs?
a. | the input force | c. | the work | b. | the output force | d. | the power |
|
|
|
20.
|
A doorknob is an example of a
a. | pulley. | c. | lever. | b. | wheel and axle. | d. | screw. |
|
|
|
21.
|
The greater the ratio of an inclined plane’s length to its height, the
greater the
a. | mechanical efficiency. | c. | work. | b. | mechanical advantage. | d. | power. |
|
Matching
|
|
|
Match each item with the correct statement below a. | watt | h. | wheel and axle | b. | machine | i. | work output | c. | work | j. | mechanical advantage | d. | mechanical efficiency | k. | joule | e. | pulley | l. | compound machine | f. | power | m. | lever | g. | work
input |
|
|
|
22.
|
comparison of a machine’s work output with work input
|
|
|
23.
|
product of the input force and distance through which it is exerted
|
|
|
24.
|
machine with a bar that pivots on a fixed point
|
|
|
25.
|
product of the output force and the distance through which it is
exerted
|
|
|
26.
|
unit used to express power
|
|
|
27.
|
device that makes work easier by changing the size or direction of a
force
|
|
|
28.
|
unit used to express energy
|
|
|
29.
|
machine with two circular devices of different sizes
|
|
|
30.
|
machine made of two or more simple machines
|
|
|
31.
|
transfer of energy that causes an object to move in the direction of the
force
|
|
|
32.
|
the rate at which work is done or energy is transformed
|
|
|
33.
|
number of times a machine multiplies force
|
|
|
34.
|
machine with a grooved wheel that holds a cable
|
|
|
Match each of the following graphics to the
type of lever it illustrates.
|
|
|
35.
|
first-class lever
|
|
|
36.
|
second-class lever
|
|
|
37.
|
third-class lever
|
Completion
Complete each
statement.
|
|
|
Use the terms from the following list to complete the sentences below.
| work input | joule | | mechanical advantage | lever | | mechanical
efficiency | compound machine | | |
|
|
|
38.
|
A block and tackle is an example of a(n) ____________________.
|
|
|
39.
|
The work you do on a machine is called ____________________.
|
|
|
40.
|
Because of friction, the ____________________ of a machine is always less than
100%.
|
|
|
41.
|
A bar that pivots on a fulcrum is called a(n) ____________________.
|
|
|
42.
|
The SI unit equivalent to 1 N x m is called a(n) ____________________.
|
Problem
|
|
|
 Figure
5-2
|
|
|
43.
|
Find the ideal mechanical advantage of the second-class lever shown in Figure
5-2.
|
|
|
44.
|
What would be the ideal mechanical advantage of the lever in Figure 5-2 if the
fulcrum were moved 2 m to the right?
|
|
|
Figure
5-3
|
|
|
45.
|
In Figure 5-3A, what is the ideal mechanical advantage of the inclined
plane?
|
|
|
46.
|
In Figure 5-3A, what is the weight of the block?
|
|
|
47.
|
In Figure 5-3A, what is the amount of work required to move the block along the
total length of the inclined plane?
|
|
|
48.
|
If the weight of the block in Figure 5-3A were doubled, how much work would be
required to move the block along the total length of the inclined plane?
|
|
|
49.
|
If the efficiency of the fixed pulley in Figure 5-3B were 100 percent, how much
force would be required in using the pulley to lift the block off the ground?
|
|
|
50.
|
A 5000-N elevator is lifted 7 m. How much work was done?
|
|
|
51.
|
A rock is lifted 0.5 m and than carried 3.5 m. What is the weight of the rock if
8 J of work were done?
|
Essay
|
|
|
52.
|
Jim used a lever to help lift a boulder from his garden. He used 50 N of input
force and achieved an output force of 250 N. He then figures the mechanical advantage using this
equation: 50 N /250 N. Will he accurately find the mechanical advantage of the lever? Explain your
answer.
|