03 Dec, 11:15AM in sunny Singapore!
Home → Homework Forum →

Physics -forces

Subscribe to Physics -forces 8 posts

Please Login or Signup to reply.
  • bonkysleuth
    bonkysleuth's Avatar
    314 posts since Mar '07
    • 10 Mar `08, 10:58AM

      when 2 forces are combined, the size of the resultant depends on the angle between the 2 forces.

       

      which of the following can not be the magnitude of the resultant when forces of magnitude 3N and 4N are combined?

       

      A 1N B 3N C 7N D 8N

       

      I wrote B-3Newton. Is that right?

       

      and secondly

       

      A force of 3.0 N and a force of 4.0 N act on an object at the same time. which of the following forces cannot be the resultant force on the object?

       

      A. 0.5 N          B. 3.5 N          c. 4.0N     D. 5.0N

       

      I wrote A. Correct me if there's any mistakes.thanks

  • airgrinder
    airgrinder's Avatar
    2,074 posts since May '01
    • 10 Mar `08, 11:06AM
      Originally posted by bonkysleuth:

      when 2 forces are combined, the size of the resultant depends on the angle between the 2 forces.

       

      which of the following can not be the magnitude of the resultant when forces of magnitude 3N and 4N are combined?

       

      A 1N B 3N C 7N D 8N

       

      I wrote B-3Newton. Is that right?

       

      and secondly

       

      A force of 3.0 N and a force of 4.0 N act on an object at the same time. which of the following forces cannot be the resultant force on the object?

       

      A. 0.5 N          B. 3.5 N          c. 4.0N     D. 5.0N

       

      I wrote A. Correct me if there's any mistakes.thanks

      I think the first one is 8N.

      I'm not sure I understand the question on the second one.

  • airgrinder
    airgrinder's Avatar
    2,074 posts since May '01
    • 10 Mar `08, 11:09AM

      For the first one, assuming 2D, absent of all other forces like gravity or friction. The max resultant force possible will be both 3N and 4N acting together in the same direction, hence 7N The min resultant force will be 3N and 4N in opposite direction, resulting a net of 1N. Hence my answer is 8N.

  • maurizio13
    maurizio13's Avatar
    12,343 posts since Sep '06
  • anakinfoo
    anakinfoo's Avatar
    640 posts since Jul '05
    • 10 Mar `08, 11:40AM

      First one is D - 8N.

      Second is A - 0.5N

       

      When two forces are acting together, the maximum resultant is when they are both pointing in the same direction.

      --->--->

      And the min. is when they are pointing towards each other.

      ---><---

      Anything in between is achievable, we just need to place them at specific angles to each other.

       

      I hope this answers your questions ><

  • aeskay
    aeskay's Avatar
    120 posts since Jun '06
    • 10 Mar `08, 12:10PM

      hmm interesting. does anyone know the explanation for the 2nd question? the question sounds pretty vague though

  • Moderator
    eagle
    eagle's Avatar
    17,973 posts since Aug '01
    • 10 Mar `08, 12:35PM
      Originally posted by anakinfoo:

      First one is D - 8N.

      Second is A - 0.5N

       

      When two forces are acting together, the maximum resultant is when they are both pointing in the same direction.

      --->--->

      And the min. is when they are pointing towards each other.

      ---><---

      Anything in between is achievable, we just need to place them at specific angles to each other.

       

      I hope this answers your questions ><

      This answer is correct.

      To further understand, draw out the vector force diagram.

  • davidche
    davidche's Avatar
    4,351 posts since May '06
    • 11 Mar `08, 10:53PM

      For the first qn, the max you can get with a 3N and 4N force is only 7 N, therefore 8N is impossible.

       

      For the second qn the lowest resultant force you can get is only 1N when 3N and 4N oppose each other.

      3N---><---4N                              

      Resultant:

      <---1N

       

      0.5N is impossible

Please Login or Signup to reply.