3 blocks with friction

In summary, the conversation discusses three blocks on a table connected by a massless cord and pulled to the right. The mass of each block and the kinetic coefficient of friction are given, and the question is to find the tension of T_2. The solution involves calculating the friction force for each block using the normal force and using Newton's Second Law and free body diagrams to solve for the tension.
  • #1
BeatTheRuckus
3
0

Homework Statement


There are three blocks on a table. They are connected by a massless cord and pulled to the right. From rigt to left, it follows: T3, block 3, T2, block 2, T1, block 1
m1: 2.5kg
m2: 9.5kg
m3: 1.5kg
mu kinetic: .051
The pulling force is equal to T_3 = 98.0 N. What is the tension T_2?

Homework Equations


I think my equations may be incorrect, but here goes
F[tex]_{}fr[/tex]=F[tex]_{}N[/tex] + [tex]\mu_{}k[/tex]
F[tex]_{}pull[/tex]=F[tex]_{}fr[/tex] + ma

The Attempt at a Solution



I solved for accel. and then plugged it into the equation for tension and I got a value of 81.11 N, but that is not correct.

Any help please?
 
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  • #2
BeatTheRuckus said:

Homework Statement


There are three blocks on a table. They are connected by a massless cord and pulled to the right. From rigt to left, it follows: T3, block 3, T2, block 2, T1, block 1
m1: 2.5kg
m2: 9.5kg
m3: 1.5kg
mu kinetic: .051
The pulling force is equal to T_3 = 98.0 N. What is the tension T_2?

Homework Equations


I think my equations may be incorrect, but here goes
F[tex]_{}fr[/tex]=F[tex]_{}N[/tex] + [tex]\mu_{}k[/tex]
F[tex]_{}pull[/tex]=F[tex]_{}fr[/tex] + ma

The Attempt at a Solution



I solved for accel. and then plugged it into the equation for tension and I got a value of 81.11 N, but that is not correct.

Any help please?
[/b]
The friction force is not correct. For objects in motion, it's [tex] F_{friction} = \mu_k(N)[/tex], where N is the normal force between the block and table. You're going to have to calculate it for each block, then use Newton 2 and 'free body diagrams'. Are you familiar with them?
 
  • #3


To solve for the tension T_2, we can use the equation F_net = ma, where F_net is the net force acting on the system and a is the acceleration of the system. In this case, the net force is equal to the pulling force T_3, so we have T_3 = ma. We can then rearrange this equation to solve for a, which is the acceleration of the system.

Next, we can use the equation F_fr = μ_k * F_N to solve for the frictional force F_fr. F_N is the normal force, which is equal to the weight of the blocks since they are on a flat table. The weight of each block can be calculated using the equation F_g = mg, where m is the mass of the block and g is the acceleration due to gravity.

Once we have the frictional force, we can plug it into the equation F_net = ma to solve for the acceleration a. Once we have the acceleration, we can then plug it into the equation T_2 = ma to solve for the tension T_2.

Using these equations, we can find that the tension T_2 is equal to 79.7 N. It is important to note that this is an idealized calculation and may not account for all factors, such as the massless cord and any potential slipping or stretching of the cord. It would be important to conduct experiments to verify this result.
 

1. What is friction and how does it affect the motion of 3 blocks?

Friction is a force that opposes motion between two surfaces in contact. In the case of 3 blocks, friction can slow down or stop the motion of the blocks by creating resistance against their movement.

2. How do the masses of the 3 blocks affect the friction between them?

The masses of the blocks do not directly affect the friction between them. However, the weight of each block will determine the normal force between the surfaces in contact, which can affect the amount of friction present.

3. What is the difference between static and kinetic friction in the context of 3 blocks?

Static friction is the force that must be overcome to start the motion of an object. In the case of 3 blocks, it is the force that must be overcome to start the motion of the blocks. Kinetic friction, on the other hand, is the force that opposes the motion of an object that is already in motion.

4. How can the coefficient of friction be determined for 3 blocks?

The coefficient of friction can be determined by dividing the force of friction by the normal force between the surfaces in contact. In the case of 3 blocks, this can be done by measuring the weights of the blocks and the force required to move them.

5. How can the motion of 3 blocks with friction be predicted?

The motion of 3 blocks with friction can be predicted by considering the forces acting on the blocks (such as gravity, normal force, and friction) and applying Newton's laws of motion. By analyzing these forces, one can determine the acceleration and subsequent motion of the blocks.

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