Help cant figure this question out

  • Thread starter camo2412
  • Start date
  • Tags
    Figure
In summary, the conversation discusses a problem involving a 20kg block attached to a 3.5kg mass by a cable, with a frictionless pulley and a coefficient of static friction of 0.2. The goal is to prove that the mass is not sufficient to start the block moving and determine the additional mass needed to do so. Through calculations, it is determined that an extra 5N or 0.5kg is needed to overcome the friction and start the motion.
  • #1
camo2412
2
0

Homework Statement


a 20kg block rests on a horizontal surface and is attatched to a mass of 3.5kg by a cable,the pulley is frictionless ans the coefficient of static frition is 0.2

prove that the mass is not suffcient to start the block moving,what is the additional mass that would be requaired to start motion


Homework Equations


http://img818.imageshack.us/img818/9962/37642403.png

The Attempt at a Solution


20kg block Ff=39.24 Fn=196.2
3.5kg block Fw=34.33
i can work out the acceleration which is 6.68 m/s

but i just don't know hwo togo about working out what it is asking to do,as in prove the mass is not sufficient to start the block moving,what additonal forceis needed

any help would be great Thanks
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
What makes a body move from rest? Can you relate to any laws?
 
Last edited:
  • #3
Hi camo2412! Welcome to Physics Forums.

I'm puzzled about the acceleration you say you have worked out. The masses won't move, because the smaller one exerts a horizontal force of (according to your figures) 34.33N, while your calculations determined that a force of 39.2N is needed to overcome the bigger block's friction.
 
  • #4
thanks nas
the acceleration calculation i did shouldn't have been in the that was another question is was working out sorry.
but yes from what i undertstand it won't move until another extra 5n is applied,
therefore i think is its an extra .5kgs that is needed
.5x9.81=4.9 which rounded up let's say 5n

just unsure if this is correct answer to the question?
 
  • #5
camo2412 said:
it won't move until another extra 5n is applied,
therefore i think is its an extra .5kgs that is needed
.5x9.81=4.9 which rounded up let's say 5n

just unsure if this is correct answer to the question?
Sounds about right to me. :smile:
 

FAQ: Help cant figure this question out

What is the question asking for?

The question is asking for assistance in solving a specific problem or understanding a concept.

What information do you need to provide in order for someone to help?

You should provide as much detail as possible about the problem or concept, including any relevant equations, data, or background information.

Is there a specific method or approach that should be used to solve the problem?

It depends on the nature of the problem. It is important to understand the underlying principles and apply them appropriately. It may also be helpful to break the problem down into smaller, more manageable steps.

Can someone else solve the problem for me?

While someone may be able to provide guidance and assistance, it is ultimately your responsibility to understand and solve the problem. This will help you develop critical thinking and problem-solving skills.

Are there any resources or tools that can help with solving the problem?

Yes, there are many resources available such as textbooks, online tutorials, and scientific calculators that can aid in understanding and solving the problem. It may also be helpful to consult with other experts in the field.

Hot Threads

Recent Insights

Back
Top