PHYSICS 131 FINAL EXAM QUESTIONS AND CORRECT DETAILED
ANSWERS (VERIFIED ANSWERS) |ALREADY GRADED
A+||BRAND NEW
A student (with a "rubbed" nail in her hand) sees another nail floating in a pan of water and
decides to test to see whether is "rubbed" also. She holds the tip of the "rubbed" nail to the tip of
the floating nail (as shown) and sees that there is an attraction between them. What can she
concluded from just this observation? - ANSWER-It is not possible to say whether the floating
nail has been rubbed or not.
The South Pole of a bar magnet is slid across a nail from its tip end to its head end. The same
process is repeated several times. How would you now describe the nail? - ANSWER-The nail is
magnetized with its tip end a South Pole and its head end a North Pole.
Based on our observation in class, what kind of objects could be involved in magnetic effects?
Choose the best answer. - ANSWER-only certain metals.
According to the alignment of tiny magnets model, which of the following drawings is the best
representation of an unmagnetized nail. - ANSWER-scrambled N and S Poles (facing different
directions).
Imagine rubbing a small nail and a large nail with the same magnet in exactly the same way.
When each magnetized nail is then brought the same distance from a magnetic compass, the
larger nail causes the compass needle to rotate further away from North than the smaller nail.
This means that the larger nail has greater magnetic strength than the smaller nail. Use the 'tiny
magnets' model to explain why. - ANSWER-In the tiny magnets model, an unmagnetized nail has
many 'tiny magnets' that each have a North and South pole. These 'tiny magnets' are flipped all
kinds of ways, pointing their north and south poles in different directions, causing there to be no
magnetization. Bigger nails have more 'tiny magnets' inside of than compared to smaller nails.
In this example, the larger nail is proven to have greater magnetic strength, since it made the
compass needle rotate further than the smaller nail. This is because the bigger nail has more
"tiny magnets' inside. Since the bigger nail has more 'tiny magnets,' when the nail is
magnetized, they all come together and point their poles to the correct end poles of the nail,
causing the magnetization strength to increase dramatically. Although the smaller nail has 'tiny
magnets,' when they line up correctly after the small nail is rubbed by a magnet, they don't have
, as much magnetic strength, because there are not as many 'tiny magnets' in the smaller nail,
since the size of the smaller nail doesn't allow it.
When a magnetized nail is cut into pieces, is each piece one-sided, two-ended, or something
different, or does the result depend on exactly where the nail is cut? What evidence supports
your answer? - ANSWER-Two-ended. When a magnetized nail is cut into pieces, the pieces can
still be magnetized, which in turn gives each end of the broken piece of nail poles. Since the nail
is broken in half, there are less 'tiny magnets,' which can cause the broken pieces to not have
as strong of a magnetic strength.
Below are two statements about contact push/pull interactions. Read each statement carefully
and decide which statements, if any, are true.
I. In a contact push/pull, interaction involving friction, where an object is slowing down, at least
one of the objects involved increases in one form of energy and decreases in another form of
energy.
II. When the kinetic energy of a moving object decreases during a contact push/pull interaction,
this means the object is an energy giver in that interaction. - ANSWER-Both I and II are true.
Below are three statements about interactions between two objects. Read each statement
carefully and decide which statements are true, based on what you have learned in Unit EM.
You may assume in each statement that the two objects are not involved n any interactions with
other objects.
I. During any interaction between two objects, one object always has a net increase in energy
and the other object always has a net decrease in energy.
II. During any interaction between two objects, the energy receiver always increases in kinetic
energy.
III. During heat interactions between two objects, the energy giver always decreases in
temperature. - ANSWER-Only I and III are true.
A person gives a shove to a wooden block, which then moves along a rough table. Below is part
of a G/R energy diagram describing the interactions between the person, block, table, and
surroundings during the launching process when both the block and table are warming up, and
both the person's hand and block are speeding up. [Assume there are insignificant changes in
temperature of the person, so you can ignore that in the energy diagram.] - ANSWER-
X=decrease in CPE and increase in KE; Y=increase in KE and TE; Z=increase in TE
ANSWERS (VERIFIED ANSWERS) |ALREADY GRADED
A+||BRAND NEW
A student (with a "rubbed" nail in her hand) sees another nail floating in a pan of water and
decides to test to see whether is "rubbed" also. She holds the tip of the "rubbed" nail to the tip of
the floating nail (as shown) and sees that there is an attraction between them. What can she
concluded from just this observation? - ANSWER-It is not possible to say whether the floating
nail has been rubbed or not.
The South Pole of a bar magnet is slid across a nail from its tip end to its head end. The same
process is repeated several times. How would you now describe the nail? - ANSWER-The nail is
magnetized with its tip end a South Pole and its head end a North Pole.
Based on our observation in class, what kind of objects could be involved in magnetic effects?
Choose the best answer. - ANSWER-only certain metals.
According to the alignment of tiny magnets model, which of the following drawings is the best
representation of an unmagnetized nail. - ANSWER-scrambled N and S Poles (facing different
directions).
Imagine rubbing a small nail and a large nail with the same magnet in exactly the same way.
When each magnetized nail is then brought the same distance from a magnetic compass, the
larger nail causes the compass needle to rotate further away from North than the smaller nail.
This means that the larger nail has greater magnetic strength than the smaller nail. Use the 'tiny
magnets' model to explain why. - ANSWER-In the tiny magnets model, an unmagnetized nail has
many 'tiny magnets' that each have a North and South pole. These 'tiny magnets' are flipped all
kinds of ways, pointing their north and south poles in different directions, causing there to be no
magnetization. Bigger nails have more 'tiny magnets' inside of than compared to smaller nails.
In this example, the larger nail is proven to have greater magnetic strength, since it made the
compass needle rotate further than the smaller nail. This is because the bigger nail has more
"tiny magnets' inside. Since the bigger nail has more 'tiny magnets,' when the nail is
magnetized, they all come together and point their poles to the correct end poles of the nail,
causing the magnetization strength to increase dramatically. Although the smaller nail has 'tiny
magnets,' when they line up correctly after the small nail is rubbed by a magnet, they don't have
, as much magnetic strength, because there are not as many 'tiny magnets' in the smaller nail,
since the size of the smaller nail doesn't allow it.
When a magnetized nail is cut into pieces, is each piece one-sided, two-ended, or something
different, or does the result depend on exactly where the nail is cut? What evidence supports
your answer? - ANSWER-Two-ended. When a magnetized nail is cut into pieces, the pieces can
still be magnetized, which in turn gives each end of the broken piece of nail poles. Since the nail
is broken in half, there are less 'tiny magnets,' which can cause the broken pieces to not have
as strong of a magnetic strength.
Below are two statements about contact push/pull interactions. Read each statement carefully
and decide which statements, if any, are true.
I. In a contact push/pull, interaction involving friction, where an object is slowing down, at least
one of the objects involved increases in one form of energy and decreases in another form of
energy.
II. When the kinetic energy of a moving object decreases during a contact push/pull interaction,
this means the object is an energy giver in that interaction. - ANSWER-Both I and II are true.
Below are three statements about interactions between two objects. Read each statement
carefully and decide which statements are true, based on what you have learned in Unit EM.
You may assume in each statement that the two objects are not involved n any interactions with
other objects.
I. During any interaction between two objects, one object always has a net increase in energy
and the other object always has a net decrease in energy.
II. During any interaction between two objects, the energy receiver always increases in kinetic
energy.
III. During heat interactions between two objects, the energy giver always decreases in
temperature. - ANSWER-Only I and III are true.
A person gives a shove to a wooden block, which then moves along a rough table. Below is part
of a G/R energy diagram describing the interactions between the person, block, table, and
surroundings during the launching process when both the block and table are warming up, and
both the person's hand and block are speeding up. [Assume there are insignificant changes in
temperature of the person, so you can ignore that in the energy diagram.] - ANSWER-
X=decrease in CPE and increase in KE; Y=increase in KE and TE; Z=increase in TE
