Go Back   Physics Help Forum > High School and Pre-University Physics Help > Kinematics and Dynamics

Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

Reply
 
LinkBack Thread Tools Display Modes
Old Feb 11th 2009, 06:49 PM   #1
Junior Member
 
Join Date: Jan 2009
Location: Longview, TX
Posts: 3
Friction Problem

I am having trouble setting up this problem in my physics HW.
I have tried many different things with the force with friction formula.
$\displaystyle F_fr=u_k*F_n$
I have tried and I don't know how to set up this problem correctly.

The problem is


Three masses, M1= 3.3 kg, M2= 4.1 kg, and M3= 7.1 kg are
made of the same material. They are on a horizontal surface
and connected by massless strings. The system accelerates
to the right at 2.43 m/sdue to an external force F pulling on M3.
Given that T1 is 17.44 N.

Calculate the coefficient of
kinetic friction μk?

Calculate the magnitude of the force F?

Thanks
chrissn13 is offline   Reply With Quote
Old Feb 12th 2009, 01:56 AM   #2
Senior Member
 
Join Date: Dec 2008
Location: Las Cruces NM
Posts: 256
I can't see which masses T1 pulls upon, but suppose it pulls to the right on m1. We are given that "the system" accelerates to the right at 2.43 meters per second, which means (I assume) that m1 has this acceleration. If T1 was the only force acting on m1, it would accelerate faster than 2.43. . So the magnitude of the frictional force on m1 must be what keeps the law force = (mass) (acceleration) true. Let mu be the coefficient of friction. (-mu m1 g + 17.44) = m1 (2.43) Similarly Suppose T1 pulls .to the left on m2. Then ( -17.44 - mu m2 g + T2) = m2 (2.43) where T2 is the tension on the next spring. For m3, we have (-T2 - mu m3 g + F) = m3 (2.43).

Thats 3 equations in the unknowns T2,F and mu. Perhaps you can solve for them, pretending the masses are known. I don't know of the masses remain in the answer or cancel out.
tashirosgt is offline   Reply With Quote
Reply

  Physics Help Forum > High School and Pre-University Physics Help > Kinematics and Dynamics

Tags
friction, problem



Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Friction Problem christineluhan Waves and Sound 1 Oct 8th 2014 01:16 AM
problem about friction panda Kinematics and Dynamics 0 Feb 1st 2014 05:42 AM
Need Help with this Friction Problem jeevankasin Kinematics and Dynamics 1 May 7th 2013 02:41 PM
Friction problem JoanF Kinematics and Dynamics 8 Dec 29th 2009 01:01 PM
Friction problem Morgan82 Kinematics and Dynamics 2 Jan 8th 2009 03:28 AM


Facebook Twitter Google+ RSS Feed