PHYS 220 (Purdue) Exam questions with
correct answers
A |pendulum |bob |swings |back |and |forth |along |a |circular |path. |Does |the |tension |in |the |string |do |any |
work |on |the |bob? |Does |gravity |do |work |on |the |bob? |- |VERIFIED |ANSWER✔✔-Only |Gravity |does |work
Imagine |that |you |are |comparing |three |different |ways |of |having |a |ball |move |down |through |the |same |
height.
In |which |case |does |the |ball |reach |the |bottom |with |the |highest |speed? |- |VERIFIED |ANSWER✔✔-
Dropping, |Sliding |on |ramp, |and |Swinging |down |are |all |the |same
A |person |raises |one |leg |to |an |angle |of |30 |degrees. |An |ankle |weight |(89 |N) |is |attached |a |distance |of |
0.84 |m |from |her |hip. |What |is |the |torque |due |to |this |weight?If |she |raises |her |leg |higher, |the |torque |
due |to |the |weight |will |- |VERIFIED |ANSWER✔✔-Decrease
Two |batons |have |equal |mass |and |length.
Which |will |be |"easier" |to |spin |about |the |center? |- |VERIFIED |ANSWER✔✔-When |mass |is |in |the |center
A |disk |of |mass |M |and |radius |R |rotates |around |the |z |axis |with |angular |velocity |ωi. |A |second |identical |
disk, |initially |not |rotating, |is |dropped |on |top |of |the |first. |There |is |friction |between |the |disks, |and |
eventually |they |rotate |together |with |angular |velocity |ωf. |- |VERIFIED |ANSWER✔✔-ωf |= |1⁄2ωi
You |are |sitting |on |a |freely |rotating |bar-stool |with |your |arms |stretched |out |and |a |heavy |glass |mug |in |
each |hand. |Your |friend |gives |you |a |twist |and |you |start |rotating |around |a |vertical |axis |though |the |
center |of |the |stool. |You |can |assume |that |the |bearing |the |stool |turns |on |is |frictionless, |and |that |there |
is |no |net |external |torque |present |once |you |have |started |spinning. |What |happens |to |the |angular |
momentum |as |you |pull |in |your |arms? |- |VERIFIED |ANSWER✔✔-stays |the |same: |no |external |forces |
gives |constant |angular |momentum
What |happens |to |your |angular |velocity |as |you |pull |in |your
arms? |- |VERIFIED |ANSWER✔✔-Increases: |"Angular |velocity |increases |because |inertia |decreases"
"Pulling |in |your |arms |decreases |your |moment |of |inertia. |Therefore, |you |will |have |an |increased |
angular |velocity"
correct answers
A |pendulum |bob |swings |back |and |forth |along |a |circular |path. |Does |the |tension |in |the |string |do |any |
work |on |the |bob? |Does |gravity |do |work |on |the |bob? |- |VERIFIED |ANSWER✔✔-Only |Gravity |does |work
Imagine |that |you |are |comparing |three |different |ways |of |having |a |ball |move |down |through |the |same |
height.
In |which |case |does |the |ball |reach |the |bottom |with |the |highest |speed? |- |VERIFIED |ANSWER✔✔-
Dropping, |Sliding |on |ramp, |and |Swinging |down |are |all |the |same
A |person |raises |one |leg |to |an |angle |of |30 |degrees. |An |ankle |weight |(89 |N) |is |attached |a |distance |of |
0.84 |m |from |her |hip. |What |is |the |torque |due |to |this |weight?If |she |raises |her |leg |higher, |the |torque |
due |to |the |weight |will |- |VERIFIED |ANSWER✔✔-Decrease
Two |batons |have |equal |mass |and |length.
Which |will |be |"easier" |to |spin |about |the |center? |- |VERIFIED |ANSWER✔✔-When |mass |is |in |the |center
A |disk |of |mass |M |and |radius |R |rotates |around |the |z |axis |with |angular |velocity |ωi. |A |second |identical |
disk, |initially |not |rotating, |is |dropped |on |top |of |the |first. |There |is |friction |between |the |disks, |and |
eventually |they |rotate |together |with |angular |velocity |ωf. |- |VERIFIED |ANSWER✔✔-ωf |= |1⁄2ωi
You |are |sitting |on |a |freely |rotating |bar-stool |with |your |arms |stretched |out |and |a |heavy |glass |mug |in |
each |hand. |Your |friend |gives |you |a |twist |and |you |start |rotating |around |a |vertical |axis |though |the |
center |of |the |stool. |You |can |assume |that |the |bearing |the |stool |turns |on |is |frictionless, |and |that |there |
is |no |net |external |torque |present |once |you |have |started |spinning. |What |happens |to |the |angular |
momentum |as |you |pull |in |your |arms? |- |VERIFIED |ANSWER✔✔-stays |the |same: |no |external |forces |
gives |constant |angular |momentum
What |happens |to |your |angular |velocity |as |you |pull |in |your
arms? |- |VERIFIED |ANSWER✔✔-Increases: |"Angular |velocity |increases |because |inertia |decreases"
"Pulling |in |your |arms |decreases |your |moment |of |inertia. |Therefore, |you |will |have |an |increased |
angular |velocity"
