CHEM 1100Ch 02 HW
CHEM 1100Ch 02 HW
Ch 02 HW
Due: 11:59pm on Thursday, February 5, 2015
To understand how points are awarded, read the Grading Policy for this assignment.
A message from your instructor...
These first two problems come from the introduction to MasteringChemistry and help you understand how to enter your answer and how the program grades
answers. Reading the information in these problems carefully and thoroughly will make your experience with MasteringChemistry less stressful and you will find
it will take you less time to complete the assignments if you write donw useful hints about the program.
Introduction to Numeric Answers with Units
This exercise is not intended to test your knowledge of any specific subject material. Therefore, on this problem you will not be penalized for using hints or
submitting incorrect answers.
Overview
When an assignment question requires that you enter an answer consisting of a numeric value and its units, you will see an answer box like the one illustrated
here.
To answer this type of question, you will need to type the numeric value and the appropriate units in the boxes provided.
To enter a numeric value, click in the Value box and then type in the value. You can enter only numeric values, including scientific notation. You
can’t enter calculations or algebraic expressions. The same grading, tolerance, and significant figure rules apply to the numeric value of your
number and units answer as apply to numeric answers.
To enter units, click in the Units box and then enter the abbreviated unit. You can enter any of the following:
A single unit such as m, eV , Å, Ω, or ∘ C.
A single unit with a prefix such as cm or MeV.
A compound unit such as ft ⋅ lb or m/s. Note that you must use explicit multiplication in compound units. For example, newton-
meters can be entered as either N ⋅ m or N−m , but not Nm.
A compound unit with a prefix such as kN ⋅ m.
To undo your work, click . To redo your work, click .
To clear your work (restart), click .
To view a list of keyboard shortcuts, click . Here are some of the most common shortcuts:
Compound unit multiplication: Type * (Shift + 8) or Type - (a hyphen).
Exponent: Type ^ (Shift + 6).
Fraction: Type / (a forward slash).
Degree symbol: Type \deg.
For more information, click ( ). To identify the purpose of any icon, simply place your cursor over it. For instance, here is an example showing
,CHEM 1100Ch 02 HW
the degree symbol:
Part A
Answer the following question by entering the numeric value with appropriate units.
If the length of one side of a square is 12.0 m, what is the perimeter of the square?
Express the perimeter to three significant figures and include the appropriate units.
,CHEM 1100Ch 02 HW
Hint 1. Definition of a perimeter
The perimeter of a square is the sum of the lengths of all four sides of the square.
ANSWER:
perimeter = 48.0 m
Correct
Because a square has four sides of equal length, the perimeter is
12 m + 12 m + 12 m + 12 m = 48.0 m
cm or km (i.e., 4800 cm or 0.0480 km)
You could also express the perimeter in equivalent units using prefixes such as
Part B
When numbers are very small or very large, it is convenient to either express the value in scientific notation and/or by using a prefix with the unit.
A pain-relieving pill has a mass of 0.005 g. Express the pill’s mass in grams using scientific notation or in milligrams.
Express your answer in scientific notation to one significant figure or use a prefix on the unit.
Hint 1. How to interpret the prefix milli
The prefix m (milli) implies multiplication by 10−3 ; thus, a milligram is 1 × 10−3 g.
ANSWER:
mass = 5×10−3 g
Correct
Because 1 milligram = 10−3 grams , you can enter your answer as 5 × 10−3 g or 5 mg.
Part C
You can also enter units that are combinations of other units. Keep in mind that you have to indicate the multiplication of units explicitly either with a
multiplication dot or a dash. You can add a multiplication dot by selecting the dot from the symbol menu.
The weight of an object is the product of its mass, m, and the acceleration of gravity, g (where g = 9.8 m/s2 ). If an object’s mass is m = 10. kg, what
is its weight?
Express the weight to two significant figures and include the appropriate units.
Hint 1. The units for weight
To calculate the weight of an object, you must multiply its mass by the acceleration due to gravity:
weight = mass of object ⋅ acceleration due to gravity
Because you are multiplying a value with the units kg by a value with the units m/s2 , find the resulting units by multiplying both units together:
(kg) ⋅ (m/s2 ) = kg ⋅ m/s2
.
ANSWER:
kg⋅m
weight = 98
s2
, CHEM 1100Ch 02 HW
Correct
The weight of the object ism ⋅ g = 98 kg ⋅ m/s2 . Because 1 kg ⋅ m/s2 = 1 N (1 newton), you can also express the answer as 98 N, in scientific
notation as 9.8 × 101 N, or with a prefix as 0.098 kN.
Part D
You can enter units that are combinations of units with prefixes. However, you must maintain the same unit system given in the problem. For example, this
question uses the SI unit system. Therefore an answer in U.S. customary units, such as miles per hour would not be accepted as correct.
A car traveling with constant speed travels 150 km in 7200 s. What is the speed of the car?
Express the speed to two significant figures and include the appropriate units.
Hint 1. The equation for computing speed
If an object is moving with constant speed, its speed is given by
distance
speed = time
ANSWER:
km
2.1×10−2 s
Correct
You can enter your answer in any equivalent combination of SI units representing a distance over any period of time. For example, you could also
enter 20.8 m/s.
Part E
You can enter compound units that are combinations of other units that are multiplied together. To enter the explicitly, type (shift + 8) on the keyboard, or
use the template in the Symbols menu.
Torque can be calculated by multiplying the force (N ) applied at 90∘ to the lever arm at a distance (m) from the pivot point (point of rotation), the
compound SI unit for the torque is N ⋅ m. If the force (at 90∘ to the lever arm) applied is 15 N and it is applied at 2.0 m from the pivot point (point of
rotation), what is the torque on the lever?
Express the torque using two significant figures and include the appropriate units.
Hint 1. The equation for computing torque
If a lever has a constant force applied at 90∘ to the lever arm at a fixed distance from the pivot point (point of rotation), the torque on the lever is
given by
torque = force (at 90∘ to lever arm) × distance to pivot point
ANSWER:
30 N⋅m
Correct
Introduction to Significant Figures
Many questions in Mastering require you to enter your answer to a specified number of significant figures. For grading purposes, some numeric answers must
be exact. Suppose you are asked "How many days are in a week?" The answer must be "7." Other numeric answers may be graded as correct not only when
they match the exact answer but also if they fall within an acceptable range of the exact answer. This range is known as the grading tolerance. Suppose you are
asked "How many days are in a year?" The precise answer is 365.24 days. However, a calendar contains 365 days, so the Mastering system will also accept
that as correct.
CHEM 1100Ch 02 HW
Ch 02 HW
Due: 11:59pm on Thursday, February 5, 2015
To understand how points are awarded, read the Grading Policy for this assignment.
A message from your instructor...
These first two problems come from the introduction to MasteringChemistry and help you understand how to enter your answer and how the program grades
answers. Reading the information in these problems carefully and thoroughly will make your experience with MasteringChemistry less stressful and you will find
it will take you less time to complete the assignments if you write donw useful hints about the program.
Introduction to Numeric Answers with Units
This exercise is not intended to test your knowledge of any specific subject material. Therefore, on this problem you will not be penalized for using hints or
submitting incorrect answers.
Overview
When an assignment question requires that you enter an answer consisting of a numeric value and its units, you will see an answer box like the one illustrated
here.
To answer this type of question, you will need to type the numeric value and the appropriate units in the boxes provided.
To enter a numeric value, click in the Value box and then type in the value. You can enter only numeric values, including scientific notation. You
can’t enter calculations or algebraic expressions. The same grading, tolerance, and significant figure rules apply to the numeric value of your
number and units answer as apply to numeric answers.
To enter units, click in the Units box and then enter the abbreviated unit. You can enter any of the following:
A single unit such as m, eV , Å, Ω, or ∘ C.
A single unit with a prefix such as cm or MeV.
A compound unit such as ft ⋅ lb or m/s. Note that you must use explicit multiplication in compound units. For example, newton-
meters can be entered as either N ⋅ m or N−m , but not Nm.
A compound unit with a prefix such as kN ⋅ m.
To undo your work, click . To redo your work, click .
To clear your work (restart), click .
To view a list of keyboard shortcuts, click . Here are some of the most common shortcuts:
Compound unit multiplication: Type * (Shift + 8) or Type - (a hyphen).
Exponent: Type ^ (Shift + 6).
Fraction: Type / (a forward slash).
Degree symbol: Type \deg.
For more information, click ( ). To identify the purpose of any icon, simply place your cursor over it. For instance, here is an example showing
,CHEM 1100Ch 02 HW
the degree symbol:
Part A
Answer the following question by entering the numeric value with appropriate units.
If the length of one side of a square is 12.0 m, what is the perimeter of the square?
Express the perimeter to three significant figures and include the appropriate units.
,CHEM 1100Ch 02 HW
Hint 1. Definition of a perimeter
The perimeter of a square is the sum of the lengths of all four sides of the square.
ANSWER:
perimeter = 48.0 m
Correct
Because a square has four sides of equal length, the perimeter is
12 m + 12 m + 12 m + 12 m = 48.0 m
cm or km (i.e., 4800 cm or 0.0480 km)
You could also express the perimeter in equivalent units using prefixes such as
Part B
When numbers are very small or very large, it is convenient to either express the value in scientific notation and/or by using a prefix with the unit.
A pain-relieving pill has a mass of 0.005 g. Express the pill’s mass in grams using scientific notation or in milligrams.
Express your answer in scientific notation to one significant figure or use a prefix on the unit.
Hint 1. How to interpret the prefix milli
The prefix m (milli) implies multiplication by 10−3 ; thus, a milligram is 1 × 10−3 g.
ANSWER:
mass = 5×10−3 g
Correct
Because 1 milligram = 10−3 grams , you can enter your answer as 5 × 10−3 g or 5 mg.
Part C
You can also enter units that are combinations of other units. Keep in mind that you have to indicate the multiplication of units explicitly either with a
multiplication dot or a dash. You can add a multiplication dot by selecting the dot from the symbol menu.
The weight of an object is the product of its mass, m, and the acceleration of gravity, g (where g = 9.8 m/s2 ). If an object’s mass is m = 10. kg, what
is its weight?
Express the weight to two significant figures and include the appropriate units.
Hint 1. The units for weight
To calculate the weight of an object, you must multiply its mass by the acceleration due to gravity:
weight = mass of object ⋅ acceleration due to gravity
Because you are multiplying a value with the units kg by a value with the units m/s2 , find the resulting units by multiplying both units together:
(kg) ⋅ (m/s2 ) = kg ⋅ m/s2
.
ANSWER:
kg⋅m
weight = 98
s2
, CHEM 1100Ch 02 HW
Correct
The weight of the object ism ⋅ g = 98 kg ⋅ m/s2 . Because 1 kg ⋅ m/s2 = 1 N (1 newton), you can also express the answer as 98 N, in scientific
notation as 9.8 × 101 N, or with a prefix as 0.098 kN.
Part D
You can enter units that are combinations of units with prefixes. However, you must maintain the same unit system given in the problem. For example, this
question uses the SI unit system. Therefore an answer in U.S. customary units, such as miles per hour would not be accepted as correct.
A car traveling with constant speed travels 150 km in 7200 s. What is the speed of the car?
Express the speed to two significant figures and include the appropriate units.
Hint 1. The equation for computing speed
If an object is moving with constant speed, its speed is given by
distance
speed = time
ANSWER:
km
2.1×10−2 s
Correct
You can enter your answer in any equivalent combination of SI units representing a distance over any period of time. For example, you could also
enter 20.8 m/s.
Part E
You can enter compound units that are combinations of other units that are multiplied together. To enter the explicitly, type (shift + 8) on the keyboard, or
use the template in the Symbols menu.
Torque can be calculated by multiplying the force (N ) applied at 90∘ to the lever arm at a distance (m) from the pivot point (point of rotation), the
compound SI unit for the torque is N ⋅ m. If the force (at 90∘ to the lever arm) applied is 15 N and it is applied at 2.0 m from the pivot point (point of
rotation), what is the torque on the lever?
Express the torque using two significant figures and include the appropriate units.
Hint 1. The equation for computing torque
If a lever has a constant force applied at 90∘ to the lever arm at a fixed distance from the pivot point (point of rotation), the torque on the lever is
given by
torque = force (at 90∘ to lever arm) × distance to pivot point
ANSWER:
30 N⋅m
Correct
Introduction to Significant Figures
Many questions in Mastering require you to enter your answer to a specified number of significant figures. For grading purposes, some numeric answers must
be exact. Suppose you are asked "How many days are in a week?" The answer must be "7." Other numeric answers may be graded as correct not only when
they match the exact answer but also if they fall within an acceptable range of the exact answer. This range is known as the grading tolerance. Suppose you are
asked "How many days are in a year?" The precise answer is 365.24 days. However, a calendar contains 365 days, so the Mastering system will also accept
that as correct.
