Balancing Forces on a String: Can Fus and Fsu be Equal and Opposite?

In summary, the conversation discusses the application of Newton's 2nd law to the system of a unicycle rider towing a surfboard carrier with a string. The concept of tension forces and their role in determining acceleration is also mentioned. The final conclusion is that Fsu and Fus are located on the string and the application of Newton's 2nd law only considers horizontal forces. The resulting acceleration is calculated to be 1.1 m/s^2.
  • #1
t_n_p
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0

Homework Statement



http://img263.imageshack.us/img263/1947/untitledtq5.jpg [Broken]

The Attempt at a Solution



Will Fus and Fsu be located on the string in equal and opposite directions?

I can do q (i) with F=ma, but unfortunately I cannot proceed to do so because I cannot answer question h!
 
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  • #2
Let's think about it. The unicycle rider is towing the surfboard carrier with a string, this creates a tension force. Now, it is the unicycle rider accelerating, and remember that in order for there to be a force two objects have to be in contact (since it's not a non-contact force in this case). Does any of this help?
 
  • #3
Yes, a massless string serves to transmit forces from its one one to the other - that is an object pulls on it and it pulls just as hard back on the object. Obviously the string cannot "generate" unequal forces at its ends - it has no internal energy source, it just transmits the force unaltered to its ends. If it does have a weight the attractive force of the Earth can alter the tensions at its ends. Also if the string drags over a surface (pulley) with friction the tension at its ends will not be the same since the interaction can change them.
 
  • #4
(h) It is "easier" to apply N2 to the system. The tension forces cancels each other out and you therefore do not need to know their values.
 
  • #5
Ok, so am I right in saying Fsu and Fus are located "on the string"?

I'm still unsure as to whether to take the system as one.. (lol, andrevdh you got in before I even finished my post!)
 
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  • #6
Minor double check: when applying Newton's 2nd to find acceleration I only take the horizontal forces, correct?!

I've even forgotten the basics!

Hence I get...

120-10=100a
110=100a
a=11/10m/s^2
 
  • #7
That is how I've got it too: 1.1 m/s^2
 
  • #8
cool thanks!
 

What is the definition of force?

Force is a physical quantity that describes the interaction between two objects. It can cause an object to accelerate, change direction, or deform.

What are the different types of forces?

There are four main types of forces: gravitational, electromagnetic, strong nuclear, and weak nuclear. Other types include friction, tension, normal, and applied forces.

What is the difference between a contact force and a non-contact force?

A contact force is a force that requires physical contact between two objects, while a non-contact force acts at a distance without any physical contact between the objects.

How do forces affect the motion of an object?

Forces can cause an object to accelerate, decelerate, or change direction. The net force acting on an object determines its motion.

How do you calculate the net force on an object?

The net force on an object can be calculated by adding all the individual forces acting on the object in the same direction, and subtracting any forces acting in the opposite direction.

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